ABA receptor agonists that modulate transpiration

ABSTRACT

The present invention provides agonist compounds that activate ABA receptors, agricultural formulations comprising the agonist compounds, and methods of use for the compounds and formulations. The agricultural formulations are useful for inducing ABA responses in plant vegetative tissues, reducing abiotic stress in plants, and inhibiting germination of plant seeds. The compounds are also useful for inducing expression of ABA-responsive genes in cells that express endogenous or heterologous ABA receptors.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application claims the benefit of U.S. Provisional Patent Application No. 62/427,064, filed Nov. 28, 2016, the contents of which are incorporated by reference herein for all purposes.

REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK

This application includes a Sequence Listing as a text file “081906-1068920-222610US-SEQLIST.txt,” machine format IBM-PC, MS-Windows operating system, created Nov. 28, 2017, and containing 225,414 bytes. The material contained in this text file is incorporated by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

Abscisic acid (ABA) is a plant hormone that regulates signal transduction associated with abiotic stress responses (Cutler et al., 2010, Abscisic Acid: Emergence of a Core Signaling Network, Annual Review of Plant Biology 61:651-679). The ABA signaling pathway has been exploited to improve plant stress response and associated yield traits via numerous approaches (Yang et al., 2010, “Narrowing Down the Targets: Towards Successful Genetic Engineering of Drought-Tolerant Crops”, Mol. Plant, 3(3):469-490). The direct application of ABA to plants improves their water use efficiency (Rademacher et al., 1987, “Water consumption and yield formation in crop plants under the influence of synthetic analogues of abscisic acid,” in: Hawkins et al. (ed.) “Plant growth regulators for agricultural and amenity use,” BCPC Monograph 36:53-66); for this reason, the discovery of ABA receptor agonists (Park et al., “Abscisic Acid Inhibits Type 2C Protein Phosphatases via the PYR/PYL Family of START Proteins,” Science, vol. 324, no. 5930, pp. 1068-1071 (2009); Melcher et al., 2010, “Identification and mechanism of ABA receptor antagonism,” Nature Structural & Molecular Biology 17(9): 1102-1110) has received increasing attention, as such molecules may be beneficial for improving crop yield (Notman, “Organic compound comes to the aid of thirsty plants”, Royal Society of Chemistry at http://www.rsc.org/chemistryworld/News/2009/May/01050901.asp (May 1, 2009; downloaded on Jun. 29, 2015)).

The first synthetic ABA receptor agonist identified was pyrabactin (Park et al., op. cit.), a naphthalene sulfonamide that efficiently activates ABA signaling in seeds, but has limited activity in vegetative tissues, where the most critical aspects of abiotic stress tolerance occur. Sulfonamides highly similar to pyrabactin have been disclosed as ABA receptor agonists (see U.S. Pat. App. Pub. No. 2013/0045952) and abiotic stress modulating compounds (see U.S. Pat. App. Pub. No. 2011/0230350). Non-sulfonamide ABA receptor agonists have also been described (see U.S. Pat. App. Pub. Nos. 2013/0045952 and 2011/0271408). A complementary approach to activating the ABA pathway involves increasing a plant's sensitivity to ABA via genetic methods. For example, conditional antisense of farnesyl transferase beta subunit gene, which increases a plant's ABA sensitivity, improves yield under moderate drought in both canola and Arabidopsis (Wang et al., 2005, “Molecular tailoring of farnesylation for plant drought tolerance and yield protection”, The Plant Journal 43(3):413-424). Thus, the manipulation of ABA signaling to improve traits contributing to yield is now well established.

It has recently been discovered that ABA elicits many of its cellular responses by binding to a soluble family of receptors called PYR/PYL proteins. PYR/PYL proteins belong to a large family of ligand-binding proteins named the START superfamily (Iyer et al., 2001, “Adaptations of the helix-grip fold for ligand binding and catalysis in the START domain superfamily,” Proteins: Structure, Function, and Bioinformatics 43(2):134-144); Ponting et al., 1999, “START: a lipid-binding domain in StAR, HD-ZIP and signalling proteins,” Trends Biochem, 24(4):130-132). These proteins contain a conserved three-dimensional architecture consisting of seven anti-parallel beta sheets, which surround a central alpha helix to form a “helix-grip” motif; together, these structural elements form a ligand-binding pocket for binding ABA or other agonists.

BRIEF SUMMARY OF THE INVENTION

The present invention provides for small molecule ABA receptor agonists, i.e., compounds that activate PYR/PYL proteins. In some aspects, the present invention provides for agricultural formulations and methods comprising the ABA receptor agonists described herein.

In some aspects, the invention presents an agricultural formulation, comprising a compound of Formula I:

wherein

-   -   R¹ is hydrogen;     -   R² is selected from hydrogen, fluoro, cyclopropyl, and R⁶;     -   Q is C(R³);     -   A¹ and A³ are independently selected from N, C(H), and C(R⁴),         wherein at least one member selected from A¹ and A³ is C(R⁴);     -   A² and A⁴ are independently selected from N and C(R⁵); wherein         at most two members selected from A¹, A², A³, and A⁴ are N;     -   R³ is cyano;     -   each R⁴ is independently selected from halo, C₁₋₃ alkyl, C₁₋₃         haloalkyl, cyclopropyl, —OR⁶, —SR⁶, and —N(R⁶)₂;     -   each R⁵ is selected from hydrogen, halo, C₁₋₃ alkyl, C₁₋₃         haloalkyl, C₃₋₇ cycloalkyl, C₁₋₆ hydroxyalkyl, nitro, —OR¹,         —SR¹, and —N(R¹)₂;     -   each R⁶ is independently selected from C₁₋₂ alkyl, C₁₋₂         haloalkyl, C₂₋₃ alkenyl, and C₂₋₃ alkynyl;     -   Z^(R) is a second ring that is selected from phenyl, naphthyl,         pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl,         pyrazolyl, thiophenyl, and thiazolyl; wherein the second ring         has from 0 to 5 R⁵ substituents;

or a salt or isomer thereof.

In some preferred embodiments, the compound of Formula I is a compound of Formula II:

wherein

-   -   R^(4a) and R^(4b) are each independently selected from hydrogen,         halo, C₁₋₃ alkyl, C₁₋₃ haloalkyl, and cyclopropyl; wherein at         least one of the R^(4a) and the R^(4b) is not hydrogen;     -   R^(5a) and R^(5b) are each independently selected from hydrogen,         halo, methyl, ethyl, trifluoromethyl, nitro, methoxy, ethoxy,         and amino;     -   m is an integer from 0 to 4;

or a salt or isomer thereof.

In some preferred embodiments, the compound of Formula I is a compound of Formula III:

wherein

-   -   R^(7a), R^(7b), R^(7c), and R^(7d) are each independently         selected from the group consisting of hydrogen, halo, C₁₋₃         alkyl, trifluoromethyl, nitro, —OR¹, and —N(R¹)₂;

or a salt or isomer thereof.

In some aspects, the invention presents a method of increasing drought tolerance in a plant, the method comprising contacting a plant with a sufficient amount of the agricultural formulation as otherwise disclosed herein, thereby increasing drought tolerance in the plant compared to not contacting the plant with the formulation.

In some aspects, the invention presents a method of bringing a plant in contact with the agricultural formulation as otherwise disclosed herein, comprising contacting the plant with the agricultural formulation.

In some aspects, the invention presents a method of activating a PYR/PYL protein, the method comprising contacting the PYR/PYL protein with a compound of Formula I, II, or III as disclosed herein.

Further aspects, objects, and advantages of the invention will become apparent upon consideration of the detailed description and figures that follow.

In some embodiments, the agricultural formulation further comprises an agricultural chemical that is useful for promoting plant growth, reducing weeds, or reducing pests. In some embodiments, the agricultural formulation further comprises at least one of a fungicide, an herbicide, a pesticide, a nematicide, an insecticide, a plant activator, a synergist, an herbicide safener, a plant growth regulator, an insect repellant, an acaricide, a molluscicide, or a fertilizer. In some embodiments, the agricultural formulation further comprises a surfactant. In some embodiments, the agricultural formulation further comprises a carrier.

In some aspects, the invention provides methods for increasing abiotic stress tolerance in a plant, the method comprising the step of contacting a plant with a sufficient amount of the above formulations to increase abiotic stress tolerance in the plant compared to the abiotic stress tolerance in the plant when not contacted with the formulation. In some embodiments, the plant is a monocot. In some embodiments, the plant is a dicot. In some embodiments, the abiotic stress tolerance comprises drought tolerance.

In some aspects, the invention provides a method of inhibiting seed germination in a plant, the method comprising the step of contacting a plant, a plant part, or a plant seed with a sufficient amount of the above formulations to inhibit germination.

In some aspects, the invention provides a plant or plant part in contact with the above formulations. In some embodiments, the plant or plant part is a seed.

In some aspects, the invention provides a method of activating a PYR/PYL protein. In some embodiments, the PYR/PYL protein binds a type 2 protein phosphatase (PP2C) polypeptide when the PYR/PYL protein binds the agonist compound quinabactin. In some embodiments, the method comprises the step of contacting the PYR/PYL protein with any of the compounds described herein.

Further aspects, objects, and advantages of the invention will become apparent upon consideration of the detailed description and figures that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A and FIG. 1B show the thermal response after 24 h elicited in adult plants by an inventive compound sprayed at 50 uM or by a solvent carrier control (Example 3).

FIG. 2 shows the luciferase activity of the compounds or a solvent carrier control in MAPKKK18:luc seedlings after 6 h treatment at 25 uM dose (Example 4).

FIG. 3A and FIG. 3B show the results of a germination study (Example 5).

FIG. 4 shows a representative thermogram and binding curve for compound Q27 (Example 6).

FIG. 5 shows changes in MAPKKK18 and RAB18 transcription levels following different chemical treatments in different genotypes (Example 7).

FIG. 6 shows the results of a test of Q27's activity with PYR1^(I110V) and reciprocal PYL2^(V114I) mutants (Example 8).

FIGS. 7A, 7B, and 7C show the calculated interactions of Q27 in PYR1 (Example 8). FIGS. 7D, 7E, and 7F show the calculated interactions of Q27 in PYL2 (Example 8).

FIG. 8A and FIG. 8C show the effects of Q27, ABA, and quinabactin in thermal response assays in an ABA-deficient aba2 mutant (Example 9). FIG. 8B shows the effects of Q27, ABA, and quinabactin in a growth complementation assay (Example 9).

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

“Agonists” are agents that, e.g., induce or activate the expression of a described target protein or bind to, stimulate, increase, open, activate, facilitate, enhance activation, sensitize or up-regulate the activity of one or more plant PYR/PYL proteins (or encoding polynucleotide). Agonists can include naturally occurring and synthetic molecules. In some embodiments, the agonists are combined with agrichemicals to produce and agricultural formulation. Examples of suitable agrichemicals include fungicides, herbicides, pesticides, fertilizers, or surfactants. Assays for determining whether an agonist “agonizes” or “does not agonize” a PYR/PYL protein include, e.g., contacting putative agonists to purified PYR/PYL protein(s) and then determining the functional effects on the PYR/PYL protein activity, as described herein, or contacting putative agonists to cells expressing PYR/PYL protein(s) and then determining the functional effects on the described target protein activity, as described herein. One of skill in the art will be able to determine whether an assay is suitable for determining whether an agonist agonizes or does not agonize a PYR/PYL protein. Samples or assays comprising PYR/PYL proteins that are treated with a putative agonist are compared to control samples without the agonist to examine the extent of effect. Control samples (untreated with agonists) are assigned a relative activity value of 100%. Agonism of the PYR/PYL protein is achieved when the activity value relative to the control is 110%, optionally 150%, optionally 200, 300%, 400%, 500%, or 1000-3000% or more higher.

The term “PYR/PYL receptor polypeptide” refers to a protein characterized in part by the presence of one or more or all of a polyketide cyclase domain 2 (PF10604), a polyketide cyclase domain 1 (PF03364), and a Bet V I domain (PF03364), which in wild-type form mediates abscisic acid (ABA) and ABA analog signaling. A wide variety of PYR/PYL receptor polypeptide sequences are known in the art. In some embodiments, a PYR/PYL receptor polypeptide comprises a polypeptide that is substantially identical to any one of SEQ ID NOs: 1-119. See, e.g., Int. Pat. Pub. No. WO 2011/139798 (U.S. Pat. App. Pub. No. US 2011/0271408).

The term “activity assay” refers to any assay that measures or detects the activity of a PYR/PYL receptor polypeptide. An exemplary assay to measure PYR/PYL receptor activity is a yeast two-hybrid assay that detects binding of a PYR/PYL polypeptide to a type 2 protein phosphatase (PP2C) polypeptide, as described in the Examples.

Two nucleic acid sequences or polypeptides are said to be “identical” if the sequence of nucleotides or amino acid residues, respectively, in the two sequences is the same when aligned for maximum correspondence as described below. The terms “identical” or percent “identity,” in the context of two or more nucleic acids or polypeptide sequences, refer to two or more sequences or subsequences that are the same or have a specified percentage of amino acid residues or nucleotides that are the same, when compared and aligned for maximum correspondence over a comparison window, as measured using one of the following sequence comparison algorithms or by manual alignment and visual inspection. When percentage of sequence identity is used in reference to proteins or peptides, it is recognized that residue positions that are not identical often differ by conservative amino acid substitutions, where amino acids residues are substituted for other amino acid residues with similar chemical properties (e.g., charge or hydrophobicity) and therefore do not change the functional properties of the molecule. Where sequences differ in conservative substitutions, the percent sequence identity may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well known to those of skill in the art. Typically this involves scoring a conservative substitution as a partial rather than a full mismatch, thereby increasing the percentage sequence identity. Thus, for example, where an identical amino acid is given a score of 1 and a non-conservative substitution is given a score of zero, a conservative substitution is given a score between zero and 1. The scoring of conservative substitutions is calculated according to, e.g., the algorithm of Meyers & Miller, Computer Applic. Biol. Sci. 4:11-17 (1988) e.g., as implemented in the program PC/GENE (Intelligenetics, Mountain View, Calif., USA).

The phrase “substantially identical,” used in the context of two nucleic acids or polypeptides, refers to a sequence that has at least 60% sequence identity with a reference sequence. Alternatively, percent identity can be any integer from 60% to 100%. Some embodiments include at least: 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94% 95%, 96%, 97%, 98%, or 99%, compared to a reference sequence using the programs described herein; preferably BLAST using standard parameters, as described below. Embodiments of the present invention provide for polypeptides, and nucleic acids encoding polypeptides, that are substantially identical to any of SEQ ID NO: 1-119.

For sequence comparison, typically one sequence acts as a reference sequence, to which test sequences are compared. When using a sequence comparison algorithm, test and reference sequences are entered into a computer, subsequence coordinates are designated, if necessary, and sequence algorithm program parameters are designated. Default program parameters can be used, or alternative parameters can be designated. The sequence comparison algorithm then calculates the percent sequence identities for the test sequences relative to the reference sequence, based on the program parameters.

A “comparison window,” as used herein, includes reference to a segment of any one of the number of contiguous positions selected from the group consisting of from 20 to 600, usually about 50 to about 200, more usually about 100 to about 150 in which a sequence may be compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned. Methods of alignment of sequences for comparison are well-known in the art. Optimal alignment of sequences for comparison can be conducted, e.g., by the local homology algorithm of Smith & Waterman, Adv. Appl. Math. 2:482 (1981), by the homology alignment algorithm of Needleman & Wunsch, J. Mol. Biol. 48:443 (1970), by the search for similarity method of Pearson & Lipman, Proc. Nat'l. Acad. Sci. USA 85:2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wis.), or by manual alignment and visual inspection.

Algorithms that are suitable for determining percent sequence identity and sequence similarity are the BLAST and BLAST 2.0 algorithms, which are described in Altschul et al. (1990) J. Mol. Biol. 215: 403-410 and Altschul et al. (1977) Nucleic Acids Res. 25: 3389-3402, respectively. Software for performing BLAST analyses is publicly available through the National Center for Biotechnology Information (NCBI) web site. The algorithm involves first identifying high scoring sequence pairs (HSPs) by identifying short words of length W in the query sequence, which either match or satisfy some positive-valued threshold score T when aligned with a word of the same length in a database sequence. T is referred to as the neighborhood word score threshold (Altschul et al, supra). These initial neighborhood word hits acts as seeds for initiating searches to find longer HSPs containing them. The word hits are then extended in both directions along each sequence for as far as the cumulative alignment score can be increased. Cumulative scores are calculated using, for nucleotide sequences, the parameters M (reward score for a pair of matching residues; always >0) and N (penalty score for mismatching residues; always <0). For amino acid sequences, a scoring matrix is used to calculate the cumulative score. Extension of the word hits in each direction are halted when: the cumulative alignment score falls off by the quantity X from its maximum achieved value; the cumulative score goes to zero or below, due to the accumulation of one or more negative-scoring residue alignments; or the end of either sequence is reached. The BLAST algorithm parameters W, T, and X determine the sensitivity and speed of the alignment. The BLASTN program (for nucleotide sequences) uses as defaults a word size (W) of 28, an expectation (E) of 10, M=1, N=−2, and a comparison of both strands. For amino acid sequences, the BLASTP program uses as defaults a word size (W) of 3, an expectation (E) of 10, and the BLOSUM62 scoring matrix (see Henikoff & Henikoff, Proc. Natl. Acad. Sci. USA 89:10915 (1989)).

The BLAST algorithm also performs a statistical analysis of the similarity between two sequences (see, e.g., Karlin & Altschul, Proc. Nat'l. Acad. Sci. USA 90:5873-5787 (1993)). One measure of similarity provided by the BLAST algorithm is the smallest sum probability (P(N)), which provides an indication of the probability by which a match between two nucleotide or amino acid sequences would occur by chance. For example, a nucleic acid is considered similar to a reference sequence if the smallest sum probability in a comparison of the test nucleic acid to the reference nucleic acid is less than about 0.01, more preferably less than about 10⁻⁵, and most preferably less than about 10⁻²⁰.

“Conservatively modified variants” applies to both amino acid and nucleic acid sequences. With respect to particular nucleic acid sequences, conservatively modified variants refers to those nucleic acids which encode identical or essentially identical amino acid sequences, or where the nucleic acid does not encode an amino acid sequence, to essentially identical sequences. Because of the degeneracy of the genetic code, a large number of functionally identical nucleic acids encode any given protein. For instance, the codons GCA, GCC, GCG and GCU all encode the amino acid alanine. Thus, at every position where an alanine is specified by a codon, the codon can be altered to any of the corresponding codons described without altering the encoded polypeptide. Such nucleic acid variations are “silent variations,” which are one species of conservatively modified variations. Every nucleic acid sequence herein which encodes a polypeptide also describes every possible silent variation of the nucleic acid. One of skill will recognize that each codon in a nucleic acid (except AUG, which is ordinarily the only codon for methionine) can be modified to yield a functionally identical molecule. Accordingly, each silent variation of a nucleic acid which encodes a polypeptide is implicit in each described sequence.

As to amino acid sequences, one of skill will recognize that individual substitutions, in a nucleic acid, peptide, polypeptide, or protein sequence which alters a single amino acid or a small percentage of amino acids in the encoded sequence is a “conservatively modified variant” where the alteration results in the substitution of an amino acid with a chemically similar amino acid. Conservative substitution tables providing functionally similar amino acids are well known in the art.

The following six groups each contain amino acids that are conservative substitutions for one another:

1) Alanine (A), Serine (S), Threonine (T);

2) Aspartic acid (D), Glutamic acid (E);

3) Asparagine (N), Glutamine (Q);

4) Arginine (R), Lysine (K);

5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and

6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W).

(see, e.g., Creighton, Proteins (1984)).

The term “plant” includes whole plants, shoot vegetative organs or structures (e.g., leaves, stems and tubers), roots, flowers and floral organs (e.g., bracts, sepals, petals, stamens, carpels, anthers), ovules (including egg and central cells), seed (including zygote, embryo, endosperm, and seed coat), fruit (e.g., the mature ovary), seedlings, plant tissue (e.g., vascular tissue, ground tissue, and the like), cells (e.g., guard cells, egg cells, trichomes and the like), and progeny of same. The class of plants that can be used in the methods of the invention includes angiosperms (monocotyledonous and dicotyledonous plants), gymnosperms, ferns, bryophytes, and multicellular and unicellular algae. It includes plants of a variety of ploidy levels, including aneuploid, polyploid, diploid, haploid, and hemizygous.

As used herein, the term “transgenic” describes a non-naturally occurring plant that contains a genome modified by man, wherein the plant includes in its genome an exogenous nucleic acid molecule, which can be derived from the same or a different plant species. The exogenous nucleic acid molecule can be a gene regulatory element such as a promoter, enhancer, or other regulatory element, or can contain a coding sequence, which can be linked to a heterologous gene regulatory element. Transgenic plants that arise from sexual cross or by selfing are descendants of such a plant and are also considered “transgenic.”.

As used herein, the term “drought-resistance” or “drought-tolerance,” including any of their variations, refers to the ability of a plant to recover from periods of drought stress (i.e., little or no water for a period of days). Typically, the drought stress will be at least 5 days and can be as long as, for example, 18 to 20 days or more (e.g., at least 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 days), depending on, for example, the plant species.

As used herein, the terms “abiotic stress,” “stress,” or “stress condition” refer to the exposure of a plant, plant cell, or the like, to a non-living (“abiotic”) physical or chemical agent that has an adverse effect on metabolism, growth, development, propagation, or survival of the plant (collectively, “growth”). A stress can be imposed on a plant due, for example, to an environmental factor such as water (e.g., flooding, drought, or dehydration), anaerobic conditions (e.g., a lower level of oxygen or high level of CO₂), abnormal osmotic conditions, salinity, or temperature (e.g., hot/heat, cold, freezing, or frost), a deficiency of nutrients or exposure to pollutants, or by a hormone, second messenger, or other molecule. Anaerobic stress, for example, is due to a reduction in oxygen levels (hypoxia or anoxia) sufficient to produce a stress response. A flooding stress can be due to prolonged or transient immersion of a plant, plant part, tissue, or isolated cell in a liquid medium such as occurs during monsoon, wet season, flash flooding, or excessive irrigation of plants, or the like. A cold stress or heat stress can occur due to a decrease or increase, respectively, in the temperature from the optimum range of growth temperatures for a particular plant species. Such optimum growth temperature ranges are readily determined or known to those skilled in the art. Dehydration stress can be induced by the loss of water, reduced turgor, or reduced water content of a cell, tissue, organ or whole plant. Drought stress can be induced by or associated with the deprivation of water or reduced supply of water to a cell, tissue, organ or organism. Salinity-induced stress (salt-stress) can be associated with or induced by a perturbation in the osmotic potential of the intracellular or extracellular environment of a cell. As used herein, the term “abiotic stress tolerance” or “stress tolerance” refers to a plant's increased resistance or tolerance to abiotic stress as compared to plants under normal conditions and the ability to perform in a relatively superior manner when under abiotic stress conditions.

A polypeptide sequence is “heterologous” to an organism or a second polypeptide sequence if it originates from a foreign species, or, if from the same species, is modified from its original form.

The terms “a,” “an,” or “the” as used herein not only include aspects with one member, but also (unless specified otherwise) include aspects with more than one member. For example, an embodiment of a method of imaging that comprises using a compound set forth in claim 1 would include an aspect in which the method comprises using two or more compounds set forth in claim 1.

“Alkenyl” as used herein includes a straight or branched aliphatic hydrocarbon group of 2 to about 15 carbon atoms that contains at least one carbon-carbon double bond. Preferred alkenyl groups have 2 to about 6 carbon atoms. More preferred alkenyl groups contain 2 to about 3 carbon atoms. “Lower alkenyl” as used herein includes alkenyl of 2 to about 6 carbon atoms. Representative alkenyl groups include vinyl, allyl, n-butenyl, 2-butenyl, 3-methylbutenyl, n-pentenyl, and the like.

“Alkoxy” as used herein includes an alkyl-O— group wherein the alkyl group is as defined herein. Representative alkoxy groups include methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, heptoxy, and the like.

“Alkyl” as used herein includes an aliphatic hydrocarbon group, which may be straight or branched-chain, having about 1 to about 20 carbon atoms in the chain. Preferred alkyl groups have 1 to 8, 1 to 6, 1 to 4, or 1 to 3 carbon atoms in the chain. “Branched-chain” as used herein includes groups in which one or more lower alkyl groups such as methyl, ethyl or propyl are attached to a linear alkyl chain (e.g., 2-methyl-3-pentyl). “Lower alkyl” as used herein includes 1 to about 6 carbon atoms in the chain, which may be straight or branched (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, t-butyl, n-pentyl, 2-pentyl, 3-pentyl, 2-methyl-2-butyl, and the like). Representative alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, n-pentyl, and 3-pentyl.

“Alkylthio” as used herein includes an alkyl-S— group wherein the alkyl group is as defined herein. Preferred alkylthio groups are those wherein the alkyl group is lower alkyl. Representative alkylthio groups include methylthio, ethylthio, isopropylthio, heptylthio, and the like.

“Alkynyl” as used herein includes a straight or branched aliphatic hydrocarbon group of 2 to about 15 carbon atoms that contains at least one carbon-carbon triple bond. Preferred alkynyl groups have 2 to about 12 carbon atoms. More preferred alkynyl groups contain 2 to about 6 carbon atoms. “Lower alkynyl” as used herein includes alkynyl of 2 to about 6 carbon atoms. Representative alkynyl groups include propynyl, 2-butynyl, 3-methylbutynyl, n-pentynyl, heptynyl, and the like.

“Amino” as used herein includes a group of formula Y₁Y₂N— wherein Y₁ and Y₂ are independently hydrogen, acyl, aryl, or alkyl; or Y₁ and Y₂, together with the nitrogen through which Y₁ and Y₂ are linked, join to form a 4- to 7-membered azaheterocyclyl group (e.g., piperidinyl). Optionally, when Y₁ and Y₂ are independently hydrogen or alkyl, an additional substituent can be added to the nitrogen, making a quaternary ammonium ion. Representative amino groups include primary amino (H₂N—), methylamino, dimethylamino, diethylamino, tritylamino, and the like. Preferably, “amino” is an —NRR′ group where R and R′ are members independently selected from the group consisting of H and alkyl. Preferably, at least one of R and R′ is H.

“Comprises” as used herein is not closed—that is, it does not limit a composition to include only the expressly disclosed components. For example, “a composition comprising A and B” could be a composition containing only A and B; a composition containing A, B, and C; a composition containing A, B, C, and D; and the like.

“Cycloalkyl” as used herein includes a non-aromatic mono- or multicyclic ring system of about 3 to about 10 carbon atoms, preferably of about 3 to about 5 carbon atoms. More preferred cycloalkyl rings include cyclopropyl. A cycloalkyl group optionally comprises at least one sp²-hybridized carbon (e.g., a ring incorporating an endocyclic or exocyclic olefin). Representative monocyclic cycloalkyl groups include cyclopentyl, cyclohexyl, cyclohexenyl, cycloheptyl, and the like. Representative multicyclic cycloalkyl include 1-decalin, norbornyl, adamantyl, and the like.

“Halo” or “halogen” as used herein includes fluoro, chloro, bromo, or iodo. A preferred halogen is fluoro.

“Haloalkyl” as used herein includes an alkyl group wherein the alkyl group includes one or more halo- substituents. For example, “fluoroalkyl” is an alkyl group wherein the alkyl group includes fluoro- substituents (e.g., trifluoromethyl).

When any two substituent groups or any two instances of the same substituent group are “independently selected” from a list of alternatives, they may be the same or different. For example, if R^(a) and R^(b) are independently selected from the group consisting of methyl, hydroxymethyl, ethyl, hydroxyethyl, and propyl, then a molecule with two R^(a) groups and two R^(b) groups could have all groups be methyl. Alternatively, the first R^(a) could be methyl, the second R^(a) could be ethyl, the first R^(b) could be propyl, and the second R^(b) could be hydroxymethyl (or any other substituents taken from the group). Alternatively, both R^(a) and the first R^(b) could be ethyl, while the second R^(b) could be hydroxymethyl (i.e., some pairs of substituent groups may be the same, while other pairs may be different).

The prefixes “u” and “μ” are used herein interchangeably to denote “micro.” For example, “uM” and “μM” are used interchangeably denote “micromolar.”

The present invention is based, in part, on the discovery of selective abscisic acid (ABA) agonists. Unlike previous ABA receptor agonists, the agonists described herein potently activate the ABA pathway in plant vegetative tissues and induce abiotic stress tolerance. The new agonists can be used to induce stress tolerance in crop species of plants. The agonists can be used to induce stress tolerance in monocot and dicot plant species, including but not limited to broccoli, radish, alfalfa, soybean, barley, and corn (maize).

Abscisic acid is a multifunctional phytohormone involved in a variety of phyto-protective functions including bud dormancy, seed dormancy or maturation, abscission of leaves and fruits, and response to a wide variety of biological stresses (e.g. cold, heat, salinity, and drought). ABA is also responsible for regulating stomatal closure by a mechanism independent of CO₂ concentration. The PYR/PYL family of ABA receptor proteins mediate ABA signaling. Plants examined to date express more than one PYR/PYL receptor protein family member, which have at least somewhat redundant activity. PYR/PYL receptor proteins mediate ABA signaling as a positive regulator in, for example, seed germination, post-germination growth, stomatal movement and plant tolerance to stress including, but not limited to, drought.

A wide variety of wild-type (naturally occurring) PYR/PYL polypeptide sequences are known in the art. Although PYR1 was originally identified as an abscisic acid (ABA) receptor in Arabidopsis, in fact PYR1 is a member of a group of at least 14 proteins (PYR/PYL proteins) in the same protein family in Arabidopsis that also mediate ABA signaling. This protein family is also present in other plants (see, e.g., SEQUENCE LISTING) and is characterized in part by the presence of one or more or all of a polyketide cyclase domain 2 (PF10604), a polyketide cyclase domain 1 (PF03364), and a Bet V I domain (PF03364). START/Bet v 1 superfamily domain are described in, for example, Radauer, BMC Evol. Biol. 8:286 (2008). In some embodiments of the methods described, a wild-type PYR/PYL receptor polypeptide comprises any of SEQ ID NOs: 1-119. In some embodiments, a wild-type PYR/PYL receptor polypeptide is substantially identical to (e.g., at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94% 95%, 96%, 97%, 98%, or 99% identical to) any of SEQ ID NOs: 1-119. In some embodiments, a PYR/PYL receptor polypeptide is substantially identical to (e.g., at least 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, 94% 95%, 96%, 97%, 98%, or 99% identical to) any of SEQ ID NO: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, or 119.

II. ABA Receptor Agonists

The present invention sets forth small-molecule ABA receptor agonists, i.e., compounds that activate PYR/PYL proteins. In some aspects, the present invention provides for agricultural formulations and methods comprising the ABA receptor agonists described herein.

In some aspects, the invention presents an agricultural formulation, comprising a compound of Formula I:

wherein

-   -   R¹ is hydrogen;     -   R² is selected from hydrogen, fluoro, cyclopropyl, and R⁶;     -   Q is C(R³);     -   A¹ and A³ are independently selected from N, C(H), and C(R⁴),         wherein at least one member selected from A¹ and A³ is C(R⁴);     -   A² and A⁴ are independently selected from N and C(R⁵); wherein         at most two members selected from A¹, A², A³, and A⁴ are N;     -   R³ is cyano;     -   each R⁴ is independently selected from halo, C₁₋₃ alkyl, C₁₋₃         haloalkyl, cyclopropyl, —OR⁶, —SR⁶, and —N(R⁶)₂;     -   each R⁵ is selected from hydrogen, halo, C₁₋₃ alkyl, C₁₋₃         haloalkyl, C₃₋₇ cycloalkyl, C₁₋₆ hydroxyalkyl, nitro, —OR¹,         —SR¹, and —N(R¹)₂;     -   each R⁶ is independently selected from C₁₋₂ alkyl, C₁₋₂         haloalkyl, C₂₋₃ alkenyl, and C₂₋₃ alkynyl;     -   Z^(R) is a second ring that is selected from phenyl, naphthyl,         pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl,         pyrazolyl, thiophenyl, and thiazolyl; wherein the second ring         has from 0 to 5 R⁵ substituents;

or a salt or isomer thereof.

In some preferred embodiments, R¹ is hydrogen. Without intending to be limited by theory, the sulfonamide may form a hydrogen bond with N173 of PYL2.

In some embodiments, R² is selected from hydrogen, fluoro, and R⁶. In some embodiments, R² is selected from hydrogen, fluoro, cycloalkyl, and R⁶. In some embodiments, R² is selected from hydrogen, fluoro, cyclopropyl, and R⁶. In some embodiments, R² is hydrogen, fluoro, C₁₋₂ alkyl, or C₁₋₂ fluoroalkyl. In some embodiments, R² is hydrogen, methyl, or trifluoromethyl. In some preferred embodiments, R² is hydrogen.

In some embodiments, A¹ is N. In some embodiments, A² is N. In some embodiments, A³ is N. In some embodiments, A⁴ is N. In some preferred embodiments, at most one member selected from A¹, A², A³, and A⁴ is N. In some preferred embodiments, no members are N. In some preferred embodiments, at most one member of the group consisting of A¹ and A³ is N.

In some preferred embodiments, R³ is a hydrogen bond acceptor, preferably —CN. Without intending to be limited by theory, the crystal structure of ABA with PYL2 suggests that positioning a hydrogen bond acceptor near the loop subdomain comprising Trp-385 is important for agonist potency. The crystal structure of quinabactin with PYL2 also suggests that the oxygen in quinabactin's dihydroquinolinone ring forms an important hydrogen bond in a “Tryp lock” hydrogen bond network formed by a water molecule, residues P92, R120 in PYL2, and W385 in HAB1. In some preferred embodiments of the present invention, a nitrile para to the sulfonamide (i.e., at R³) can coordinate with the loop subdomain. In some embodiments, the present invention sets forth a method of coordinating a hydrogen-bond acceptor with the PYR/PYL loop subdomain by administering a composition of Formula I.

In some embodiments, R⁴ is independently selected from halo, C₁₋₃ alkyl, C₁₋₃ haloalkyl, cyclopropyl, —OR⁶, —SR⁶, and —N(R⁶)₂. In some embodiments, R⁴ is independently selected from C₁₋₃ alkyl, cyclopropyl, —OR⁶, and —N(R⁶)₂. In some embodiments, R⁴ is independently selected from C₁₋₃ alkyl, cyclopropyl, and —OR⁶. In some embodiments, R⁴ is independently selected from methyl, ethyl, isopropyl, propyl, cyclopropyl, and —OR⁶, wherein R⁶ is C₁₋₃ alkyl. In some preferred embodiments, R⁴ is independently selected from methyl, ethyl, propyl, methoxy, and ethoxy. In some preferred embodiments, R⁴ is independently selected from methyl and methoxy. In some preferred embodiments, R⁴ is methyl.

In some embodiments, Z^(R) is naphthyl. In some embodiments, Z^(R) is pyridyl. In some embodiments, Z^(R) is pyrazinyl. In some embodiments, Z^(R) is pyrimidinyl. In some embodiments, Z^(R) is pyridazinyl. In some embodiments, Z^(R) is pyrrolyl. In some embodiments, Z^(R) is pyrazolyl. In some embodiments, Z^(R) is thiophenyl. In some embodiments, Z^(R) is thiazolyl. In some embodiments, Z^(R) is selected from phenyl, naphthyl, and pyridyl. In some preferred embodiments, Z^(R) is phenyl.

In some preferred embodiments, the compound is a compound of Formula II:

wherein

-   -   R^(4a) and R^(4b) are each independently selected from hydrogen,         halo, C₁₋₃ alkyl, C₁₋₃ haloalkyl, and cyclopropyl; wherein at         least one of the R^(4a) and the R^(4b) is not hydrogen;     -   R^(5a) and R^(5b) are each independently selected from hydrogen,         halo, methyl, ethyl, trifluoromethyl, nitro, methoxy, ethoxy,         and amino;     -   m is an integer from 0 to 4;

or a salt or isomer thereof.

Without intending to be limited by theory, the electron density on the ring bearing the nitrile may be important in determining activity towards one or both of the PYR1 and PYL2 receptors. Some embodiments with alkoxy and alkyl substitution ortho- to the nitrile provided better activity with PYR1 and PYL2 as compared to halogen or trifluoromethyl substitution, especially bis-trifluoromethyl substitution.

In some preferred embodiments, at least one substituent ortho- to R³ is electron-donating. In some preferred embodiments, at least on substituent ortho- to R³ is C₁-C₄ alkyl, cyclopropyl, or C₁-C₄ alkoxy (e.g., methyl, ethoxy, methoxy, ethyl, propyl, and cyclopropyl).

In some preferred embodiments, no more than one ring substituent ortho- to R³ is halo or haloalkyl. In some preferred embodiments, no ring substituent ortho- to R³ is halo or haloalkyl. In some preferred embodiments, no ring substituent ortho- to R³ is electron-withdrawing (e.g., nitro, perfluoroalkyl, carboxy, halo, and the like).

In some preferred embodiments, each ring substituent ortho- to R³ is selected independently from the group consisting of methyl, ethyl, n-propyl, chloro, bromo, trifluoromethyl, methoxy, and ethoxy.

In some embodiments, each ring substituent meta- to R³ is selected independently from the group consisting of hydrogen, nitro, and —N(R⁶)₂. In some embodiments, each ring substituent meta- to R³ is hydrogen or —N(R⁶)₂ (preferably, hydrogen).

In some preferred embodiments, no more than one ring substituent (i.e., R^(4a), R^(4b), R^(5a), or R^(5b)) is halo, haloalkyl, nitro, or —SR¹. In some embodiments, no ring substituent is halo, haloalkyl, nitro, or —SR¹. In some embodiments, no ring substituent is electron-withdrawing (e.g., halo, haloalkyl, or nitro).

One structural feature present in quinabactin is the n-propyl group attached to the dihydroisoquinolinone ring. Without intending to be limited by theory, during binding with PYL2, the n-propyl group is thought to extend into a small hydrophobic cleft, which is known as the 3′ tunnel and is lined with the L87, F61, and V163 residues. In some preferred embodiments, a small hydrophobic substituent ortho to the R³ nitrile may occupy this cleft.

In some preferred embodiments, at least one ring substituent ortho- to R³ is a small hydrophobic substituent, such as a C₁₋₃ alkyl group (e.g., methyl). In some embodiments, both substituents are small, hydrophobic substituents (e.g., dimethyl; methyl and methoxy).

In some embodiments, R^(5a) and R^(5b) are each independently selected from hydrogen, halo, methyl, ethyl, trifluoromethyl, nitro, methoxy, ethoxy, and amino. In some embodiments, R^(5a) and R^(5b) are each independently selected from hydrogen, halo, methyl, ethyl, trifluoromethyl, and methoxy. In some embodiments, R^(5a) and R^(5b) are each independently selected from hydrogen, halo, and methyl. In some preferred embodiments, R^(5a) and R^(5b) are hydrogen. In some preferred embodiments, R^(5b) is hydrogen.

In some preferred embodiments, m is 1 or 2 (e.g., 1). In some embodiments, m is 0. In some embodiments, m is 1. In some embodiments, m is 2. In some embodiments, m is 3. In some embodiments, m is 4. In some embodiments, m is 5 (e.g., perfluorophenyl).

In some preferred embodiments, the compound of Formula I or II is a compound of Formula III:

wherein

-   -   R^(7a), R^(7b), R^(7c), and R^(7d) are each independently         selected from the group consisting of hydrogen, halo, C₁₋₃         alkyl, cyclopropyl, trifluoromethyl, nitro, —OR¹, and —N(R¹)₂;

or a salt or isomer thereof.

In some embodiments, R^(7a) and R^(7b) are each independently selected from halo, nitro, C₁₋₃ alkyl, cyclopropyl, —OR⁶, and —N(R⁶)₂. In some preferred embodiments, R^(7a) is hydrogen or halo. In some preferred embodiments, R^(7a) is hydrogen.

In some preferred embodiments, R^(7b) is not hydrogen. In some preferred embodiments, R^(7b) is C₁₋₃ alkyl (e.g., methyl). Without intending to be limited by theory, the calculated position of a methyl group in a 4-methylbenzyl substituent superimposes well with the C-6 methyl group in abscisic acid (ABA).

In some preferred embodiments, R^(7c) and R^(7d) are hydrogen. In some embodiments, R^(7a), R^(7c), and R^(7d) are hydrogen.

The compounds described above can be synthesized using methods known in the art. For example, methods of synthesis are set forth in Intl. Pat. Publ. Nos. WO 2007/068418 A1 and WO 2009/120826 A1; U.S. Pat. App. Publ. Nos. US 2009/0215728 A1 and US 2012/0028923 A1; European Pat. Publ. No. EP 2172456 A1; and Li, Xun et al. Organic Process Research and Development 2009, 13(3), 652-55 as described in U.S. Pat. Nos. 5,498,755 and 6,127,382.

III. ABA Receptor Agonist Formulations

The present invention provides for agricultural chemical formulations formulated for contacting to plants, wherein the formulation comprises an ABA receptor agonist of the present invention. In some embodiments, the plants that are contacted with the agonists comprise or express an endogenous PYR/PYL polypeptide. In some embodiments, the plants that are contacted with the agonists do not comprise or express a heterologous PYR/PYL polypeptide (e.g., the plants are not transgenic or are transgenic but express heterologous proteins other than heterologous PYR/PYL proteins). In some embodiments, the plants that are contacted with the agonists do comprise or express a heterologous PYR/PYL polypeptide as described herein.

In some embodiments, the invention presents the agricultural formulation as otherwise disclosed herein, further comprising at least one of a fungicide, an herbicide, a pesticide, a nematicide, an insecticide, a plant activator, an herbicide safener, a plant growth regulator, an insect repellant, an acaricide, a molluscicide, or a fertilizer.

In some embodiments, the invention presents the agricultural formulation as otherwise disclosed herein, further comprising a surfactant. In some embodiments, the invention presents the agricultural formulation as otherwise disclosed herein, further comprising a a carrier.

In some embodiments, the agricultural formulation further comprises an agricultural chemical that is useful for promoting plant growth, reducing weeds, or reducing pests. In some embodiments, the agricultural formulation further comprises at least one of a fungicide, an herbicide, a pesticide, a nematicide, an insecticide, a plant activator, a synergist, an herbicide safener, a plant growth regulator, an insect repellant, an acaricide, a molluscicide, or a fertilizer.

In some aspects, the invention provides a plant or plant part in contact with the ABA receptor agonist compounds or ABA receptor agonist formulations described herein. In some embodiments, the plant is a seed.

The formulations can be suitable for treating plants or plant propagation material, such as seeds, in accordance with the present invention, e.g., in a carrier. Suitable additives include buffering agents, wetting agents, coating agents, polysaccharides, and abrading agents. Exemplary carriers include water, aqueous solutions, slurries, solids, and dry powders (e.g., peat, wheat, bran, vermiculite, clay, pasteurized soil, many forms of calcium carbonate, dolomite, various grades of gypsum, bentonite and other clay minerals, rock phosphates and other phosphorous compounds, titanium dioxide, humus, talc, alginate and activated charcoal). Any agriculturally suitable carrier known to one skilled in the art would be acceptable and is contemplated for use in the present invention.

In some embodiments, the formulations can also include at least one surfactant, herbicide, fungicide, pesticide, or fertilizer. In some embodiments, the agricultural chemical formulation comprises at least one of a surfactant, an herbicide, a pesticide, such as but not limited to a fungicide, a bactericide, an insecticide, an acaricide, and a nematicide, a plant activator, a synergist, an herbicide safener, a plant growth regulator, an insect repellant, or a fertilizer. In some embodiments, the agricultural chemical formulation comprises at least one of an herbicide, a fungicide, a bactericide, an insecticide, an acaricide, a nematicide, and an insect repellent. In some embodiments, the agricultural chemical formulation comprises a plant activator, an herbicide safener, a plant growth regulator, an insect repellant, or a fertilizer.

In some embodiments, the agricultural chemical formulation comprises an effective amount of one or more herbicides selected from the group consisting of paraquat (592), mesotrione (500), sulcotrione (710), clomazone (159), fentrazamide (340), mefenacet (491), oxaziclomefone (583), indanofan (450), glyphosate (407), prosulfocarb (656), molinate (542), triasulfuron (773), halosulfuron-methyl (414), and pretilachlor (632). The above herbicidal active ingredients are described, for example, in “The Pesticide Manual,” 12th ed., C. D. S. Tomlin (ed.), British Crop Protection Council, 2000, under the entry numbers added in parentheses; for example, mesotrione (500) is described therein under entry number 500. The above compounds are described, for example, in U.S. Pat. No. 7,338,920, which is incorporated by reference herein in its entirety.

In some embodiments, the agricultural chemical formulation comprises an effective amount of one or more fungicides selected from the group consisting of: sedaxane, fludioxonil, penthiopyrad, prothioconazole, flutriafol, difenoconazole, azoxystrobin, captan, cyproconazole, cyprodinil, boscalid, diniconazole, epoxiconazole, fluoxastrobin, trifloxystrobin, metalaxyl, metalaxyl-M (mefenoxam), fluquinconazole, fenarimol, nuarimol, pyrifenox, pyraclostrobin, thiabendazole, tebuconazole, triadimenol, benalaxyl, benalaxyl-M, benomyl, carbendazim, carboxin, flutolanil, fuberizadole, guazatine, myclobutanil, tetraconazole, imazalil, metconazole, bitertanol, cymoxanil, ipconazole, iprodione, prochloraz, pencycuron, propamocarb, silthiofam, thiram, triazoxide, triticonazole, tolylfluanid, and a manganese compound (such as mancozeb, maneb). In some embodiments, the agricultural chemical formulation comprises an effective amount of one or more of an insecticide, an acaricide or nematcide selected from the group consisting of: thiamethoxam, imidacloprid, clothianidin, lamda-cyhalothrin, tefluthrin, beta-cyfluthrin, permethrin, abamectin, fipronil, and spinosad. Details (e.g., structure, chemical name, commercial names, etc) of each of the above pesticides with a common name can be found in the e-Pesticide Manual, version 3.1, 13th Edition, Ed. CDC Tomlin, British Crop Protection Council, 2004-05. The above compounds are described, for example, in U.S. Pat. No. 8,124,565, which is incorporated by reference herein in its entirety.

In some embodiments, the agricultural chemical formulation comprises an effective amount of one or more fungicides selected from the group consisting of cyprodinil (i.e., (4-cyclopropyl-6-methyl-pyrimidin-2-yl)-phenyl-amine) (208), dodine (289); chlorothalonil (142); folpet (400); prothioconazole (685); boscalid (88); proquinazid (682); dithianon (279); fluazinam (363); ipconazole (468); and metrafenone. Some of the above compounds are described, for example, in “The Pesticide Manual” [The Pesticide Manual—A World Compendium; Thirteenth Edition; Editor: C. D. S. Tomlin; The British Crop Protection Council, 2003], under the entry numbers added in parentheses. The above compounds are described, for example, in U.S. Pat. No. 8,349,345, which is incorporated by reference herein in its entirety.

In some embodiments, the agricultural chemical formulation comprises an effective amount of one or more fungicides selected from fludioxonil, metalaxyl and a strobilurin fungicide, or a mixture thereof. In some embodiments, the strobilurin fungicide is azoxystrobin, picoxystrobin, kresoxim-methyl, or trifloxystorbin. In some embodiments, the agricultural chemical formulation comprises an effective amount of one or more of an insecticide selected from a phenylpyrazole and a neonicotinoid. In some embodiments, the phenylpyrazole is fipronil and the neonicotinoid is selected from thiamethoxam, imidacloprid, thiacloprid, clothianidin, nitenpyram and acetamiprid. The above compounds are described, for example, in U.S. Pat. No. 7,071,188, which is incorporated by reference herein in its entirety. In some embodiments, the agricultural chemical formulation comprises an effective amount of one or more biological pesticide, including but not limited to, Pasteuria spp., Paeciliomyces, Pochonia chlamydosporia, Myrothecium metabolites, Muscodor volatiles, Tagetes spp., bacillus firmus, including bacillus firmus CNCM I-1582.

IV. Application to Plants

The ABA receptor agonist formulations and compositions can be applied to plants using a variety of known methods, e.g., by spraying, atomizing, dipping, pouring, irrigating, dusting or scattering the compositions over the propagation material, or brushing or pouring or otherwise contacting the compositions over the plant or, for a seed, by coating, encapsulating, spraying, dipping, immersing the seed in a liquid composition, or otherwise treating the seed. In an alternative to directly treating a plant or seed before planting, the formulations of the invention can also be introduced into the soil or other media into which the seed is to be planted. For example, the formulations can be introduced into the soil by spraying, scattering, pouring, irrigating or otherwise treating the soil.

In some embodiments, a carrier is also used. The carrier can be solid or liquid, as noted above. In some embodiments peat is suspended in water as a carrier of the ABA receptor agonist, and this mixture is sprayed into the soil or planting media or over the seed as it is planted.

The types of plant that can be treated with the ABA receptor agonists described herein include both monocotyledonous (i.e., monocot) and dicotyledonous (i.e., dicot) plant species including cereals such as barley, rye, sorghum, tritcale, oats, rice, wheat, soybean and corn; beets (for example, sugar beet and fodder beet); cucurbits including cucumber, muskmelon, canteloupe, squash and watermelon; cale crops including broccoli, cabbage, cauliflower, bok choi, and other leafy greens, other vegetables including tomato, pepper, lettuce, beans, pea, onion, garlic and peanut; oil crops including canola, peanut, sunflower, rape, and soybean; solanaceous plants including tobacco; tuber and root crops including potato, yam, radish, beets, carrots and sweet potatoes; fruits including strawberry; fiber crops including cotton and hemp; other plants including coffee, bedding plants, perennials, woody ornamentals, turf and cut flowers including carnation and roses; sugar cane; containerized tree crops; evergreen trees including fir and pine; deciduous trees including maple and oak; and fruit and nut trees including cherry, apple, pear, almond, peach, walnut and citrus.

It will be understood that the ABA receptor agonists described herein mimic the function of ABA on cells. Thus, it is expected that one or more cellular responses triggered by contacting the cell with ABA will also be triggered be contacting the cell with the ABA receptor agonists described herein. The ABA receptor agonists described herein mimic the function of ABA and are provided in a useful formulation.

In some aspects, the invention presents a method of bringing a plant in contact with the agricultural formulation as otherwise disclosed herein, comprising contacting the plant with the agricultural formulation.

V. Methods of Increasing Abiotic Stress Tolerance in Plants

The present invention also provides methods of increasing abiotic stress tolerance in a plant. Thus, in some embodiments, a plant is contacted with an ABA receptor agonist described herein, or an ABA receptor agonist formulation, in sufficient amount to increase the abiotic stress tolerance in the plant. The amount of the ABA receptor agonist formulation applied to the plant can be sufficient to increase the abiotic stress tolerance compared to not contacting the plant with the ABA receptor agonist formulation. The plant can be contacted with the ABA formulation using any of the methods described herein. The increase in abiotic stress tolerance can improve the plants growth or survival to abiotic stress conditions that adversely effect the plant's growth or survival. Abiotic stress includes physical or chemical conditions described herein, but preferably is drought resistance or drought tolerance.

In some embodiments, application of the ABA receptor agonists or ABA receptor agonist formulations described herein increases the abiotic stress resistance of a plant.

In some aspects, the invention presents a method of increasing drought tolerance in a plant, the method comprising contacting a plant with a sufficient amount of the agricultural formulation as otherwise disclosed herein, thereby increasing drought tolerance in the plant compared to not contacting the plant with the formulation.

In some aspects, the invention provides methods for increasing abiotic stress tolerance in a plant, the method comprising the step of contacting a plant with a sufficient amount of the above formulations to increase abiotic stress tolerance in the plant compared to the abiotic stress tolerance in the plant when not contacted with the formulation. In some embodiments, the plant is a monocot. In some embodiments, the plant is a dicot. In some embodiments, the abiotic stress tolerance comprises drought tolerance.

Abiotic stress resistance can assayed according to any of a number of well-known techniques. For example, for drought tolerance, plants can be grown under conditions in which less than optimum water is provided to the plant. Drought resistance can be determined by any of a number of standard measures including turgor pressure, growth, yield, and the like.

VI. Methods of Inhibiting Seed Germination in a Plant

The present invention also provides methods of inhibiting seed germination. Thus, in some embodiments, a plant, plant part, or a seed is contacted with an ABA receptor agonist formulation in an amount sufficient to inhibit seed germination. The seed can be contacted with the ABA receptor agonist formulation using any of the methods described herein. In some embodiments, the seed is directly contacted with the ABA receptor agonist formulation. In some embodiments, the ground or soil is contacted with the ABA receptor agonist formulation either prior to or after planting or sowing the seeds. In some embodiments, a plant is contacted with sufficient ABA receptor agonist formulation to inhibit germination of seeds that later develop from the plant.

In some aspects, the invention provides a method of inhibiting seed germination in a plant, the method comprising the step of contacting a plant, a plant part, or a plant seed with a sufficient amount of the above formulations to inhibit germination. In some embodiments, application of the ABA receptor agonists described herein to seeds inhibits germination of the seeds.

VII. Methods of Activating PYR/PYL Receptor Polypeptides

The present invention also provides methods of activating a PYR/PYL receptor polypeptide. In some embodiments, a PYR/PYL polypeptide is contacted with a compound described above, and the activated PYR/PYL polypeptide binds to a PP2C polypeptide. In some embodiments, the PYR/PYL polypeptide is capable of being activated by the agonist compound quinabactin. In some embodiments, the PYR/PYL protein that is activated is substantially identical to any one of SEQ ID NOs:1-119. Examples of sequences of ABA receptors from various plants are provided in U.S. Pat. App. Pub. 2011/0271408, which is incorporated by reference herein in its entirety.

In some aspects, the invention provides a method of activating a PYR/PYL protein. In some embodiments, the method comprises the step of contacting the PYR/PYL protein with any of the compounds described herein (e.g., a compound of Formula I, II, or III as disclosed herein).

In some embodiments, the PYR/PYL protein is expressed by a cell. In some embodiments, the PYR/PYL protein is expressed by a plant cell. In some embodiments, the PYR/PYL protein is an endogenous protein. In some embodiments, the PYR/PYL protein is a heterologous protein. In some embodiments, the cell further expresses a type 2 protein phosphatase (PP2C). In some embodiments, the type 2 protein phosphatase is HAB1 (Homology to ABI1), ABI1 (Abscisic acid insensitive 1), or ABI2 (Abscisic acid insensitive 2).

In some embodiments, the method activates a PYR/PYL receptor in a cell free in vitro assay. In some embodiments, the method activates a PYR/PYL receptor expressed in a cell. In some embodiments, the cell is a plant cell. In some embodiments, the cell is an animal or mammalian cell. In some embodiments, the cell expresses an endogenous PYR/PYL protein. In some embodiments, the cell is engineered to express a heterologous PYR/PYL polypeptide. In some embodiments, the cell expresses a heterologous PP2C polypeptide. In some embodiments, the cell expresses a PP2C polypeptide selected from HAB1 (homology to ABI1), ABI1, or ABI2.

In some embodiments, the activated PYR/PYL polypeptide induces expression of heterologous genes. In some embodiments, the heterologous genes are ABA-responsive genes. In some embodiments, the induced gene expression occurs in cells that express an endogenous PYR/PYL polypeptide. In some embodiments, the induced gene expression occurs in cells that express a heterologous PYR/PYL polypeptide.

VIII. Screening for New ABA Receptor Agonists and Antagonists

For the present invention, an agent agonizes a PYR/PYL receptor if, when the agent is present at a concentration no greater than 200 μM, contacting the agent to the PYR/PYL receptor results in activation or up-regulation of the activity of the PYR/PYL receptor. If an agent does not induce activation or up-regulation of a PYR/PYL receptor protein's activity when the agent is present at a concentration no greater than 200 μM, then the agent does not significantly agonize the PYR/PYL receptor.

As used herein, “activation” requires a minimum threshold of activity to be induced by the agent. Determining whether this minimum threshold of activity has been met can be accomplished, e.g., by using an enzymatic phosphatase assay that sets a minimum value for the level of enzymatic activity that must be induced, or by using an enzymatic phosphatase assay in the presence of a colorimetric detection reagent (e.g., para-nitrophenylphosphate) wherein the minimum threshold of activity has been met if a color change is observed.

A number of different screening protocols can be utilized to identify agents that agonize or antagonize a PYR/PYL polypeptide. Screening can take place using isolated, purified or partially purified reagents. In some embodiments, purified or partially purified PYR/PYL polypeptide can be used.

Alternatively, cell-based methods of screening can be used. For example, cells that naturally-express a PYR/PYL polypeptide or that recombinantly express a PYR/PYL polypeptide can be used. In some embodiments, the cells used are plant cells, animal cells, bacterial cells, fungal cells, including but not limited to yeast cells, insect cells, or mammalian cells. In general terms, the screening methods involve screening a plurality of agents to identify an agent that modulates the activity of a PYR/PYL polypeptide by, e.g., binding to PYR/PYL polypeptide, or activating a PYR/PYL polypeptide or increasing expression of a PYR/PYL polypeptide, or a transcript encoding a PYR/PYL polypeptide.

1. PYR/PYL Polypeptide Binding Assays

Optionally, preliminary screens can be conducted by screening for agents capable of binding to a PYR/PRL polypeptide, as at least some of the agents so identified are likely PYR/PYL polypeptide modulators.

Binding assays can involve contacting a PYR/PYL polypeptide with one or more test agents and allowing sufficient time for the protein and test agents to form a binding complex. Any binding complexes formed can be detected using any of a number of established analytical techniques. Protein binding assays include, but are not limited to, methods that measure co-precipitation or co-migration on non-denaturing SDS-polyacrylamide gels, and co-migration on Western blots (see, e.g., Bennet, J. P. and Yamamura, H. I. (1985) “Neurotransmitter, Hormone or Drug Receptor Binding Methods,” in Neurotransmitter Receptor Binding (Yamamura, H. I., et al., eds.), pp. 61-89). Other binding assays involve the use of mass spectrometry or NMR techniques to identify molecules bound to PYR/PYL polypeptide or displacement of labeled substrates (e.g., labeled ABA). The PYR/PYL polypeptide protein utilized in such assays can be naturally expressed, cloned or synthesized.

2. Activity

PYR/PYL polypeptide agonists can be identified by screening for agents that activate or increase activity of a PYR/PYL polypeptide. Antagonists can be identified by reducing activity.

One activity assay involves testing whether a candidate agonist can induce binding of a PYR/PYL protein to a type 2 protein phosphatase (PP2C) polypeptide in an agonist-specific fashion. Mammalian or yeast two-hybrid approaches (see, e.g., Bartel, P. L. et. al. Methods Enzymol, 254:241 (1995)) can be used to identify polypeptides or other molecules that interact or bind when expressed together in a cell. In some embodiments, agents that agonize a PYR/PYL polypeptide are identified in a two-hybrid assay between a PYR/PYL polypeptide and a type 2 protein phosphatase (PP2C) polypeptide (e.g., ABI1 or 2 or orthologs thereof, e.g., from the group A subfamily of PP2Cs), wherein an ABA receptor agonist is identified as an agent that activates or enables binding of the PYR/PYL polypeptide and the PP2C polypeptide. Thus, the two polypeptides bind in the presence, but not in the absence of the agent. In some embodiments, a chemical compound or agent is identified as an agonist of a PYR/PYL protein if the yeast cell turns blue in the yeast two hybrid assay,

The biochemical function of PYR1, and PYR/PYL proteins in general, is to inhibit PP2C activity. This can be measured in live cells using the yeast two hybrid or other cell-based methods. It can also be measured in vitro using enzymatic phosphatase assays in the presence of a colorimetric detection reagent (for example, para-nitrophenylphosphate). The yeast-based assay used above provides an indirect indicator of ligand binding. To address this potential limitation, one can use in vitro competition assays, or cell based assays using other organisms, as alternate approaches for identifying weak binding target compounds.

3. Expression Assays

Screening for a compound that increases the expression of a PYR/PYL polypeptide is also provided. Screening methods generally involve conducting cell-based or plant-based assays in which test compounds are contacted with one or more cells expressing PYR/PYL polypeptide, and then detecting an increase in PYR/PYL expression (either transcript or translation product). Assays can be performed with cells that naturally express PYR/PYL or in cells recombinantly altered to express PYR/PYL, or in cells recombinantly altered to express a reporter gene under the control of the PYR/PYL promoter.

Various controls can be conducted to ensure that an observed activity is authentic including running parallel reactions with cells that lack the reporter construct or by not contacting a cell harboring the reporter construct with test compound.

4. Validation

Agents that are initially identified by any of the foregoing screening methods can be further tested to validate the apparent activity or determine other biological effects of the agent. In some cases, the identified agent is tested for the ability to effect plant stress (e.g., drought tolerance), seed germination, or another phenotype affected by ABA. A number of such assays and phenotypes are known in the art and can be employed according to the methods of the invention.

EXAMPLES Example 1: Preparation of 4-Cyanophenyl Sulfonamides

A small library of sulfonamide analogs was assembled via a coupling reaction between various substituted 4-cyanoanilines (5-19) and 4-substituted benzylsulfonyl chloride (Scheme 1). While anilines 5-9 were commercially available, anilines 10, 11 and 13-16 were synthesized according to protocols specified in the literature. Aniline 17 and 19 were synthesized using high-yielding Suzuki coupling reactions with either triethylborane or cyclopropylboronic acids using substrates 16. Negishi coupling reactions were performed with substrates 7 and 16, using n-propylzincbromide solution to yield anilines 12 and 18.

General Procedures

Unless stated otherwise, all reactions were carried out under an atmosphere of argon in oven-dried glassware. Indicated reaction temperatures refer to those of the reaction bath, while room temperature (RT or rt) is noted as 25° C. All other solvents were of commercially available anhydrous quality and used as received. Pure reaction products were typically dried under high vacuum. Commercially available starting materials and reagents were used as received unless specified otherwise. Analytical thin layer chromatography (TLC) was performed with (5×20 cm, 60 Å, 250 μm). Visualization was accomplished using a 254 nm UV lamp.

Intermediates 5, 6, 7, 8, 9, 20, and several substituted benzyl sulfonyl chlorides listed in the reagents and conditions section were commercially available. Intermediates 10, 11, 13-15, and 24 were synthesized according literature protocols given in Int'l Pat. Pub. No. WO 2007/068418 A1/U.S. Pat. App. Pub. No. 2008/0312230 (compound 10), Int'l Pat. Pub. No. WO 2009/120826 A1/U.S. Pat. App. Pub. No. 2009/0270363 (compound 11), U.S. Pat. App. Pub. Nos. US 2009/0215728 A1 and 2012/0028923 A1, as well as European Pat. Pub. No. EP 2172456 A1/U.S. Pat. App. Pub. No. 2010/0179172 (compounds 13-15); and Li, Xun; Ng, Raymond; Zhang, YongSheng; Russel, Ronald; Sui, Zhihua. Organic Process Research and Development 2009, 13(3), 652-55 (compound 24).

¹H NMR spectra were recorded on a 400 MHz spectrophotometer. Chemical shifts are reported in ppm with the solvent resonance as internal standard ([DMSO-d6 2.5 ppm] for ¹H, ¹³C respectively). Data are reported as follows: chemical shift, multiplicity (s=singlet, d=doublet, dd=doublet of doublet, t=triplet, q=quartet, br=broad, m=multiplet), number of protons, and coupling constants. All compounds submitted for biological testing were found to be ≥95% pure.

General Procedure for Sulfonamide Coupling Reaction

To a cold solution of aryl amine (1 equiv) in anhydrous DCM was added (3 equiv) of diisopropylethylamine followed by the desired sulfonyl chloride. The solution was stirred for 12 h, and the reaction was quenched by adding dilute hydrochloric acid (2N). The reaction mixture was extracted in dichloromethane, dried over anhydrous sodium sulfate, and concentrated in vacuo. The residue was purified by silica gel flash chromatography using a hexanes/ethyl acetate gradient from 0%-50% to yield pure compounds as yellowish white powders in 60-80% yields.

Exemplary Procedure for Suzuki Coupling with Triethylborane

Triethylborane solution (8.36 mL, 2.8 equiv) was added to a solution of aryl bromide, amine 16 (0.63 g, 1 equiv), Pd(dppf)Cl₂ (43.2 mg, 0.02 equiv), and CsOAc (1.15 g, 2.0 equiv) in THF. The mixture was heated at reflux overnight until all the starting material was consumed. After cooling, the reaction mixture was diluted with ethyl acetate and washed with sodium bicarbonate solution and brine, dried over anhydrous sodium sulfate, and concentrated. The residue was purified by silica gel flash chromatography with a hexanes/ethyl acetate gradient from 0%-60%, which yielded 17 (0.4 g) as a white solid in 85% yield.

General Procedure for Suzuki Coupling with Cyclopropylboronic Acid

To a solution of 16 or Q22 (1 equiv), boronic acid (2.5 equiv), potassium phosphate (4.0 equiv), and tricylohexylphosphine (0.1 equiv) in toluene/water (1:20 v/v) was added palladium actetate (0.05 equiv). The mixture was heated at 100° C. overnight and then cooled to room temperature. Water was added to the reactions, and the mixture was extracted with ethyl acetate; the combined extracts were washed with brine, dried over anhydrous sodium sulfate, and concentrated in vacuo. The residue was purified using silica gel flash chromatography to afford 19 and Q23 as white solids in 75% and 70% yields respectively.

General Procedure for Negishi Coupling

To a solution of aryl bromide 7 or 16 (1 equiv), Pd(OAc)₂ (0.05 equiv), and XPhos (0.1 equiv) at 0° C. was added a solution of n-propylzinc bromide (1.8 equiv) in THF. The mixture was then heated in an oil bath at 50° C. for 2 h. The reaction was cooled and quenched slowly by addition of water, the reaction mixture was extracted with ethyl acetate, and the combined extracts were dried over sodium sulfate and concentrated in vacuo. The residue was purified by silica gel flash chromatography using a hexanes/ethyl acetate gradient to yield anilines 12 and 18 in 65% and 60% yields respectively.

General Procedure for Reduction of Nitro Derivatives

To a cold solution of the aryl nitro derivative (1 equiv) in methanol, was added ammonium formate (10 equiv), followed by slow addition of powdered zinc dust (10 equiv). The reaction was stirred for 30 min and concentrated in vacuo. The residue was adsorbed on silica gel and purified using flash chromatography (hexanes/ethyl acetate gradient from 0-60%) to yield products in near-quantitative yields.

Procedure for Reductive Amination for Synthesis of Amine 23

To a cold solution of amine 22 (500 mg, 1 equiv) in 3 mL of 3 M H₂SO₄ was added n-propanal (130 uL, 1.2 equiv). The mixture was stirred for 30 min at 0° C.; thereafter, sodium borohydride (137 mg, 2.5 equiv) was added portionwise, and the reaction was slowly brought to room temperature over 6 h. The reaction was quenched with saturated bicarbonate solution and extracted with ethyl acetate; the combined extracts were dried over sodium sulfate and concentrated in vacuo. The residue was purified using silica gel flash chromatography to yield the yellowish product in 70% yield.

General Procedure for Synthesis of Amides Q10 and Q11

To a cold solution of anilines 22 or 23 (1 equiv) in pyridine was added acetyl chloride (1.5 equiv). The reaction was stirred for 3 h and then diluted with water. The reaction mixture was extracted with three times with ethyl acetate, and the combined extracts were dried over sodium sulfate and concentrated in vacuo. The residue was purified using silica gel flash chromatography to yield off-white powders Q10 and Q11 in 75% and 78% yield respectively.

Synthesis of Intermediate 26 Via Diazotization/Cyanation of 25

To a solution of CuCN (1.94 g, 2.5 equiv), in acetonitrile (50 mL) was added t-butyl nitrite (2.06 mL, 2.0 equiv). The mixture was cooled to 0° C. and intermediate 25 (2 g, 1 equiv) was added portionwise over 10 min. The mixture was heated for 2 h at 70° C., quenched with a 10% solution of sodium carbonate, and the pH was adjusted to 11 using a 1 M solution of NaOH. The reaction was extracted with ethyl acetate; the combined organic extracts were washed with brine, dried over sodium sulfate, and concentrated in vacuo. The residue was purified using flash chromatography using hexanes/ethyl acetate gradient (0-50%) to give compound as a yellow solid in 65% yield.

N-(4-Cyano-3-methylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q1)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.25 (s, 3H) 2.37 (s, 3H) 4.52 (s, 2H) 6.99-7.07 (m, 2H) 7.07-7.14 (m, 4H) 7.63 (d, J=8.58 Hz, 1H), 10.31 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₆N₂O₂S found 318.1312.

N-(3-Chloro-4-cyanophenyl)-1-(4-methylphenyl)methanesulfonamide (Q2)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.25 (s, 3H) 4.60 (s, 2H) 7.05-7.18 (m, 6H) 7.79 (d, J=8.58 Hz, 1H) 10.62 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₅H₁₃ClN₂O₂S found 338.0721.

N-(3-Bromo-4-cyanophenyl)-1-(4-methylphenyl)methanesulfonamide (Q3)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.25 (s, 3H) 4.59 (s, 2H) 7.05-7.20 (m, 5H) 7.26 (d, J=2.34 Hz, 1H) 7.76 (d, J=8.58 Hz, 1H) 10.58 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₅H₁₃BrN₂O₂S found 384.0338.

N-(4-Cyano-3-(trifluoromethyl)-phenyl)-1-(4-methylphenyl)methanesulfonamide (Q4)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.21 (s, 3H) 4.63 (s, 2H) 7.01-7.15 (m, 4H) 7.31-7.41 (m, 2H) 7.96 (d, J=7.80 Hz, 1H) 10.79 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₃F₃N₂O₂S found 372.0968.

N-(4-Cyano-3-methoxyphenyl)-1-(4-methylphenyl)methanesulfonamide (Q20)

¹H NMR (400 MHz, DMSO-d6) d ppm 2.25 (s, 3H) 3.79 (s, 3H) 4.55 (s, 2H) 6.72-6.85 (m, 2H) 7.11 (s, 4H) 7.58 (d, J=8.58 Hz, 1H) 10.36 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₆N₂O₃S found 334.1262.

N-(4-Cyano-3-ethoxyphenyl)-1-(4-methylphenyl)methanesulfonamide (Q26)

¹H NMR (400 MHz, DMSO-d6) δ ppm 1.33 (t, J=7.02 Hz, 3H) 2.25 (s, 3H) 4.03 (d, J=7.02 Hz, 2H) 4.54 (s, 2H) 6.72-6.83 (m, 2H) 7.10 (s, 4H) 7.57 (d, J=8.58 Hz, 1H) 10.33 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₇H₁₈N₂O₃S found 348.1458.

N-(4-Cyano-3-ethylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q29)

¹H NMR (400 MHz, DMSO-d6) δ ppm 1.15 (t, J=7.80 Hz, 3H) 2.24 (s, 3H) 2.67 (q, J=7.28 Hz, 2H) 4.52 (s, 2H) 7.02-7.14 (m, 6H) 7.63 (d, J=8.58 Hz, 1H) 10.31 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₇H₁₈N₂O₂S found 332.1511.

N-(4-Cyano-3-propylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q31)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.89 (t, J=7.41 Hz, 3H) 1.57 (m, 2H) 2.24 (s, 3H) 2.63 (t, J=8 Hz, 2H) 4.51 (s, 2H) 7.01-7.13 (m, 6H) 7.64 (d, J=8.58 Hz, 1H) 10.30 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₈H₂₀N₂O₂S found 346.1654.

N-(4-Cyano-3-cyclopropylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q27)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.56-0.65 (m, 2H) 1.03-1.12 (m, 2H) 2.03-2.12 (m, 1H) 2.22 (s, 3H) 4.48 (s, 2H) 6.63 (d, J=2.34 Hz, 1H) 6.99-7.13 (m, 5H) 7.61 (d, J=8.58 Hz, 1H) 10.22 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₈H₁₈N₂O₂S found 344.1499.

N-(4-Cyano-3, 5-dimethylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q15)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.25 (s, 3H) 2.35 (s, 6H) 4.52 (s, 2H) 6.85 (m, 2H) 7.10 (m, 4H) 10.22 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₇H₁₈N₂O₂S found 332.1523.

N-(4-Cyano-3, 5-(bistrifluoromethyl)phenyl)-1-(4-methylphenyl) methanesulfonamide (Q14)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.18 (s, 3H) 4.73 (s, 2H) 7.00 (d, J=8.58 Hz, 2H) 7.11-7.27 (m, 3H) 7.52 (s, 2H) 11.20 (br. s., 1H) ESI HRMS [M+NH₄]⁺ for C₁₇H₁₂F₆N₂O₂S found 440.0778.

N-(3-Bromo-4-cyano-5-methylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q25)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.25 (s, 3H) 2.39 (s, 3H) 4.59 (s, 2H) 7.14-7.10 (m, 6H) 10.49 (s, 1H)) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₅BrN₂O₂S found 398.0362.

N-(4-Cyano-3-ethyl-5-methylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q30)

¹H NMR (400 MHz, DMSO-d6) δ ppm 1.14 (t, J=7.41 Hz, 3H) 2.24 (s, 3H) 2.35 (s, 3H) 2.66 (q, J=7.80 Hz, 2H) 4.52 (s, 2H) 6.87 (d, J=6.24 Hz, 2H) 7.10 (s, 4H) 10.23 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₈H₂₀N₂O₂S found 346.1640.

N-(4-Cyano-3-methyl-5-propylphenyl)-1-(4-methylphenyl)methanesulfonamide (Q32)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.87 (t, J=8 Hz, 3H) 1.55 (m, 2H) 2.24 (s, 3H) 2.35 (s, 3H) 2.62 (t, J=8 Hz, 2H) 4.51 (s, 2H) 6.81-6.92 (m, 2H) 7.09 (m, 4H) 10.22 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₉H₂₂N₂O₂S found 360.1831.

N-(4-Cyano-3-cyclopropyl-5-methylphenyl)-1-(4-methylphenyl) methanesulfonamide (Q28)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.54-0.64 (m, 2H) 0.99-1.09 (m, 2H) 2.01-2.12 (m, 1H) 2.27 (s, 3H) 2.35 (s, 3H) 4.48 (s, 2H) 6.41-6.48 (m, 1H) 6.84 (s, 1H) 7.04-7.11 (m, 4H) 10.13 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₉H₂₀N₂O₂S found 358.1586.

1-(4-Chlorophenyl)-N-(4-cyano-3,5-dimethylphenyl)methanesulfonamide (Q22)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.36 (s, 6H) 4.62 (s, 2H) 6.86 (s, 2H) 7.20-7.27 (m, 2H) 7.33-7.40 (m, 2H) 10.28 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₅ClN₂O₂S found 352.0886.

N-(4-Cyano-3,5-dimethylphenyl)-1-(4-cyclopropylphenyl)methanesulfonamide (Q23)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.54-0.64 (m, 2H) 0.88-0.96 (m, 2H) 1.79-1.90 (m, 1H) 2.34 (s, 6H) 4.51 (s, 2H) 6.83 (s, 2H) 6.98 (d, J=7.80 Hz, 2H) 7.09 (d, J=7.80 Hz, 2H) 10.22 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₉H₂₀N₂O₂S found 358.1707.

1-(4-Bromo-2-fluorophenyl)-N-(4-cyano-3,5-dimethylphenyl)methanesulfonamide (Q24)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.35 (s, 6H) 4.63 (s, 2H) 6.87 (m, 2H) 7.30 (t, J=8.19 Hz, 1H) 7.41 (dd, J=7.80, 1.56 Hz, 1H) 7.49 (dd, J=9.36, 1.56 Hz, 1H) 10.44 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₄BrFN₂O₂S found 416.0266.

N-[4-Cyano-3-(trifluoromethyl)phenyl]-1-(4-nitrophenyl)methanesulfonamide (Q5)

¹H NMR (400 MHz, DMSO-d6) δ ppm 4.94 (s, 2H) 7.39-7.47 (m, 2H) 7.51-7.59 (m, 2H) 8.02 (d, J=8.58 Hz, 1H) 8.10-8.18 (m, 2H) 10.97 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₅H₁₀F₃N₃O₄S found 403.0688.

1-(4-Aminophenyl)-N-[4-cyano-3-(trifluoromethyl)phenyl]methanesulfonamide (Q6)

¹H NMR (400 MHz, DMSO-d6) δ ppm 4.41 (s, 2H) 6.40 (d, J=8.58 Hz, 2H) 6.83 (d, J=8.58 Hz, 2H) 7.33-7.49 (m, 2H) 7.96 (d, J=8.58 Hz, 1H) ESI HRMS [M+NH₄]⁺ for C₁₅H₁₂F₃N₃O₂S found 373.0946.

1-(4-Bromophenyl)-N-[4-cyano-3-(trifluoromethyl)phenyl]methanesulfonamide (Q7)

¹H NMR (400 MHz, DMSO-d6) δ ppm 4.71 (s, 2H) 7.16-7.26 (m, 2H) 7.37-7.51 (m, 4H) 7.99 (d, J=7.80 Hz, 1H) 10.85 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₅H₁₀BrF₃N₂O₂S found 437.9921.

N-[4-Cyano-3-(trifluoromethyl)phenyl]-1-[4-(trifluoromethyl)phenyl]methanesulfonamide (Q9)

¹H NMR (400 MHz, DMSO-d6) δ ppm 4.87 (s, 2H) 7.37-7.44 (m, 2H) 7.49 (m, J=8.58 Hz, 2H) 7.63 (m, J=7.80 Hz, 2H) 7.97 (d, J=8.58 Hz, 1H) 10.91 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₀F₆N₂O₂S found 426.0710.

N-[4-{[(4-Methylbenzyl)sulfonyl]amino}-2-(trifluoromethyl)phenyl]acetamide (Q10)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.03 (s, 3H) 2.25 (s, 3H) 4.47 (s, 2H) 7.06-7.18 (m, 4H) 7.28-7.34 (m, 3H) 9.42 (br. s., 1H) 10.10 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₇H₁₇F₃N₂O₃S found 404.1255.

N-[4-{[(4-Methylbenzyl)sulfonyl]amino}-2-(trifluoromethyl)phenyl]-N-propylacetamide (Q11)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.83 (t, J=7.41 Hz, 3H) 1.41-1.55 (m, 2H) 1.80 (s, 3H) 2.31 (s, 3H) 3.10 (q, J=6.24 Hz, 2H) 4.93 (s, 2H) 5.69 (s, 1H) 6.12 (d, J=2.34 Hz, 1H) 6.67 (d, J=9.36 Hz, 1H) 6.93 (dd, J=8.58, 2.34 Hz, 1H) 7.18-7.25 (m, 4H) ESI HRMS [M+NH₄]⁺ for C₂₀H₂₃F₃N₂O₃S found 446.1725.

N-(4-Cyano-3-methylphenyl)-1-[4-(trifluoromethyl)phenyl]methanesulfonamide (Q13)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.36 (s, 3H) 4.75 (s, 2H) 7.00-7.10 (m, 2H) 7.46 (d, J=7.80 Hz, 2H) 7.58-7.72 (m, 3H) 10.41 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₃F₃N₂O₂S found 372.0993.

N-[2-Amino-4-cyano-5-(trifluoromethyl)phenyl]-1-(4-methylphenyl) methanesulfonamide (Q18)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.23 (s, 3H) 4.46 (s, 2H) 6.18 (br. s., 2H) 7.07 (d, J=7.80 Hz, 2H) 7.12-7.22 (m, 3H) 7.30 (s, 1H) 9.30 (br. s., 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₄F₃N₃O₂S found 387.1102.

N-[4-Cyano-2-nitro-5-(trifluoromethyl)phenyl]-1-(4-methylphenyl) methanesulfonamide (Q17)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.16 (s, 3H) 4.66 (s, 2H) 7.01 (d, J=7.80 Hz, 2H) 7.16-7.24 (m, 2H) 7.36 (s, 1H) 8.60 (s, 1H) ESI HRMS [M+NH₄]⁺ for C₁₆H₁₂F₃N₃O₄S found 417.0844.

4-Amino-2-ethyl-6-methylbenzonitrile (17)

¹H NMR (400 MHz, DMSO-d6) δ ppm 1.12 (t, J=8.0 Hz, 3H) 2.24 (s, 3H) 2.55 (q, J=7.28 Hz, 2H) 5.91 (s, 2H) 6.30 (m, 2H).

4-Amino-2-methyl-6-propylbenzonitrile (18)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.87 (t, J=8.0 Hz, 3H) 1.49-1.59 (m, 2H) 2.24 (s, 3H) 2.51 (d, J=7.80 Hz, 2H) 5.90 (s, 2H) 6.24-6.33 (m, 2H).

4-Amino-2-cyclopropyl-6-methylbenzonitrile (19)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.54-0.63 (m, 2H) 0.90-1.01 (m, 2H) 1.92-2.01 (m, 1H) 2.24 (s, 3H) 5.84 (s, 2H) 5.94 (d, J=1.56 Hz, 1H) 6.26 (d, J=1.56 Hz, 1H).

4-Amino-2-propylbenzonitrile (12)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.87 (t, J=7.41 Hz, 3H) 1.55 (m, 2H) 2.52 (t, J=7.80 Hz, 2H) 6.00 (br. s., 2H) 6.39-6.48 (m, 2H) 7.24-7.32 (m, 1H).

1-(4-Methylphenyl)-N-[4-nitro-3-(trifluoromethyl)phenyl]methanesulfonamide (21)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.21 (s, 3H) 4.64 (s, 2H) 7.05 (m, J=7.80 Hz, 2H) 7.13 (m, J=7.80 Hz, 2H) 7.35-7.47 (m, 2H) 8.06 (d, J=8.58 Hz, 1H) 10.82 (s, 1H).

N-[4-Amino-3-(trifluoromethyl)phenyl]-1-(4-methylphenyl)methanesulfonamide (22)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.26 (s, 3H) 4.25 (s, 2H) 5.46 (s, 2H) 6.77 (d, J=9.36 Hz, 1H) 7.02-7.16 (m, 6H) 9.31 (s, 1H).

1-(4-Methylphenyl)-N-[4-(propylamino)-3-(trifluoromethyl)phenyl]methanesulfonamide (23)

¹H NMR (400 MHz, DMSO-d6) δ ppm 0.87 (t, J=7.41 Hz, 3H) 1.43-1.61 (m, 2H) 2.26 (s, 3H) 3.09 (q, J=6.76 Hz, 2H) 4.25 (s, 2H) 5.19 (t, J=5.46 Hz, 1H) 6.75 (d, J=9.36 Hz, 1H) 7.09-7.17 (m, 5H) 7.21 (dd, J=9.36, 2.34 Hz, 1H) 9.35 (s, 1H).

2-Bromo-6-methyl-4-nitrobenzonitrile (26)

¹H NMR (400 MHz, DMSO-d6) δ ppm 2.63 (s, 3H) 8.34 (d, J=2.34 Hz, 1H) 8.45 (d, J=2.34 Hz, 1H).

Example 2: PP2C Inhibition Assays

The compounds from Example 1 were screened against PYR1 and PYL2 using recombinant receptors and PP2C using an absorbance based assay with p-nitrophenolphosphate as a substrate for the PP2C (Table 1). The newly synthesized ligands exhibited activity ranging from 48 nM to 8242 nM on PYR1 and 969 nM to 31400 nM on PYL2.

TABLE 1 IC₅₀s of various analogs of the Q series on the PYR1 and PYL2 receptor. PYR1 PYL2 MIC (μM) Thermal Ligand R^(4a) R³ R^(4b) R^(5b) R^(7b) R^(7b) (nM) (nM) Germination Response Q1 Me CN H H H Me 246 ± 60 20000 ± 1080 10 − Q2 Cl CN H H H Me 3909 ± 122 >50000 25 − Q3 Br CN H H H Me 2504 ± 151 >50000 >25 − Q4 CF₃ CN H H H Me 258 ± 19 9581 ± 102 10 − Q20 OMe CN H H H Me 130 ± 9  11793 ± 1122 5 − Q26 OEt CN H H H Me 112 ± 15 7459 ± 469 10 ++ Q29 Et CN H H H Me   48 ± 0.3 2695 ± 64  5 + Q31 nPr CN H H H Me  100 ± 0.4 2909 ± 270 10 + Q27 Δ CN H H H Me 87 ± 3 3266 ± 13  5 +++ Q15 Me CN Me H H Me 98 ± 7 2583 ± 222 10 + Q14 CF₃ CN CF₃ H H Me >50000 >50000 >25 − Q25 Br CN Me H H Me 355 ± 34 16700 ± 788  25 − Q30 Me CN Et H H Me  72 ± 15 969 ± 77 10 +++ Q32 Me CN nPr H H Me 220 ± 18 1605 ± 23  10 + Q28 Me CN Δ H H Me 210 ± 36 1656 ± 46  10 − Q22 Me CN Me H H Cl 197 ± 9  5633 ± 800 10 − Q23 Me CN Me H H Δ 203 ± 25 20140 ± 1457 10 − Q25 Me CN Me H F Br 188 ± 19 11853 ± 1473 10 − Q5 CF₃ CN H H H NO₂ 8242 ± 520 >50000 >25 − Q6 CF₃ CN H H H NH₂ 3400 ± 200 >50000 >25 − Q7 CF₃ CN H H H Br  326 ± 7.7 31400 ± 3400 10 − Q9 CF₃ CN H H H CF₃ 3400 ± 270 >50000 10 − Q10 CF₃ NHAc H H H Me >50000 >50000 >25 − Q11 CF₃ N(nPr)Ac H H H Me >50000 >50000 >25 − Q13 Me CN H H H CF₃ 1102 ± 183 >50000 >25 − Q17 CF₃ CN H NO₂ H Me >50000 >50000 >25 − Q18 CF₃ CN H NH₂ H Me >50000 >50000 >25 − ABA — — — — — —  111 ± 3.8   39 ± 2.3 1 ++ QB — — — — — —   85 ± 6.9 211 ± 41 3 +++ MIC: Minimal Inhibitory Concentration; NA: Not active; QB: Quinabactin; Δ: Cyclopropyl substituent

PP2C activity assays using recombinant receptors and PP2Cs were carried out as follows: Purified proteins were pre-incubated for 30 minutes at room temperature in 160 μl assay buffer (100 mM Tris-HCl-pH 7.9, 100 mM NaCl, 3 μg bovine serum albumin, and 0.1% 2-mercaptoethanol) containing 1 mM MnCl₂ with quinabactin or compounds of Example 1. Reactions were started by adding 40 μL of a reaction solution containing 25 mM 4-nitrophenyl phosphate in assay buffer, after which absorbance measurements were immediately collected using a 405 nm on Wallac plate reader. Reactions contained 100 nM PP2C and 200 nM PYR/PYL proteins. For IC₅₀ calculation, the different concentration of quinabactin or Example 1 compound from 50 μM to 4 nM were used to measure PP2C activity. The dose response data was fitted to a log (inhibitor) vs response-(variable slope) model using non-linear regression to infer the IC₅₀ values using Graph Pad Prism 6.0.

Example 3: Thermal Imaging Assays

Molecules that elicit ABA-like effects in vivo typically close guard cells, which arrests transpirational water loss, resulting in less efficient cooling of the leaf surface and a concomitant increase in leaf surface temperature. Infrared thermography has recently emerged as an attractive, noninvasive technique to evaluate plant leaf surface temperature. When sprayed at 50 uM dose on adult Arabidopsis plants, the compounds Q26, Q27, Q30 and (to a lesser extent) Q29, Q31, and Q32 were able to increase the leaf surface temperature significantly and comparably to the changes elicited by quinabactin and ABA at the same dose (Table 1 and FIG. 1A).

For the adult plants used for thermal imaging, seeds were sterilized as described in Example 3. Afterwards, the seeds were spread onto 0.7% agar MS plant growth medium containing one-half MS salts and 0.5% sucrose. After 4 d of stratification at 4° C., these plates were transferred to a growth chamber in light and allowed to germinate and grow for 7 d. The seedlings then were transferred into soil, and plants of 3-4 wk old were used for thermal imaging. Before thermal imaging, topical spraying of the plants was performed with a water solution containing an active agent (50 μM ABA, quinabactin, or a test compound of interest), 0.5% DMSO, and 0.02% polyalkyleneoxide modified heptamethyltrisiloxane surfactant (Silwet-77). Thermal images were collected just before spraying, 24 h after treatment, and 48 h after treatment. Treated plants were compared to mock-treated plants that had been sprayed with water containing 0.5% DMSO and 0.02% Silwet-77.

Thermal images were collected at 16 h after treatment. Thermal images were quantified using the Flir tools software version 5.2.15161.1001 by measuring the average leaf temperature of 5-6 leaves per plant. Average temperatures were calculated for 10 replicate plants (in 5 pots) per treatment. Statistical comparisons between the treated and the mock-treated plants were performed using pairwise t-tests. In the graphs represented in FIG. 1B, error bars represent the standard error of mean, asterisks symbols indicate statistical significance, and * indicates p≤0.05, ** for p≤0.01, *** for p≤0.001.

Example 4: pMAPKKK18::LUC⁺ Assays

To assess the tissue-level response induced by the ligands, transgenic Arabidopsis plants were constructed in which an ABA responsive promoter (MAPKKK18, see Okamoto, M. et al., “Activation of Dimeric ABA Receptors Elicits Guard Cell Closure, ABA-Regulated Gene Expression, and Drought Tolerance,” Proc. Natl. Acad. Sci. 2013, 110 (29), 12132-12137) drives expression of an enhanced luciferase (Luc⁺). Q26, Q27, and Q29-Q32 induced a significant luciferase response in the pMAPKKK18::Luc⁺ line, indicating the compounds activate an ABA transcriptional response (FIG. 2).

pMAPKKK18::Luc⁺ activity was measured with 8-d-old seedlings that had been grown in plant growth liquid medium (½ MS plant growth medium and 0.5% sucrose) under 16-h-light and 8-h-dark conditions. Seedlings were transferred to new plant growth liquid medium with the test chemical at 25 μM concentration and 100 μM luciferin. Luciferase assay image were taken at 6 h in the dark by camera (SONY α a7s) with FE1.8/55 lense (FE 55 mm F1.8 ZA; SEL55F18Z).

Example 5: Germination Assays

Germination experiments were performed with Arabidopsis thaliana seeds of wildtype Col0, Ler, or mutant backgrounds.

Seeds were sterilized by 30 sec incubation in 70% ethanol solution followed by a 5 min inhibition (while vigorously shaking) in a bleach-Tween solution. Afterwards, the sterilizing solutions were removed, and five washes were performed with sterile distilled water. To enhance complete removal of the solutions between the different steps, short centrifuge spins were performed. Finally, the now surface-sterilized seeds were re-suspended in an aseptic 0.1% agar solution to simplify distribution over multiwall plates. One drop of the solution contained on average 20-30 seeds.

In the multiwell plates, seeds were plated onto 0.7% agar Murashige amd Skoog (MS) plant growth medium containing one-half MS salts and 0.5% sucrose containing different concentrations of ABA, quinabactin, or the compound of interest. After 4 d of stratification at 4° C., the plates were transferred to a growth chamber in darkness and allowed to germinate for 3 d before germination was evaluated. The results are shown above in Table 1 and FIGS. 3A and 3B.

Example 6: Thermodyanamic Parameters for Binding of PYR1 to Q27

Thermodyanamic parameters for binding of PYR1 to Q27 (“CB/cyanabactin”) were determined using a Nano ITC Low Volume calorimeter, with the data acquisition software ITCRun v3.2 and data analysis software NanoAnalyze v3.6.

Reverse titration experiments were performed due to the low ligand solubility at 35° C. All solutions were degassed to avoid bubbles and equilibrated to the corresponding temperature for each experiment. The ligand solution in the calorimetric cell was titrated with PYR1 protein in dialysis buffer [aqueous 100 mM 3-(N-morpholino)propanesulfonic acid (MOPS), 1 mM β-mercaptoethanol, pH 7.0]. PYR1 was assayed at protein concentrations from 300-450 uM, and the Q26 ligand dissolved in dialysis buffer was assayed at concentrations between 15-30 uM. The titrations were done in a series of 20 injections of 2.5 ul each. The heat produced from each injection was acquired from the integration of the calorimetric peak. The heat due to protein-ligand binding was obtained as the difference between the heat of the reaction and the corresponding heat of dilution from buffer into Q27 ligand.

The resulting binding isotherms were analyzed by blank constant fitting of the data to an independent one-site sites model with NanoAnalyze. FIG. 4 shows a representative thermogram and binding curve. Data shown are the average of three independent experiments±standard error.

Example 7: qRT-PCR Analysis of Compound Q27

To further investigate if Q27/CB, quinabactin/QB and ABA treatments induced ABA-responsive genes in vegetative tissues, qRT-PCR analysis was performed.

A plant RNA purification kit (Invitrogen) was used to isolate total RNA from plant tissue as per manufacturer's instructions. A QantiTec reverse transcription kit was used to synthesize cDNA from 1 μg of total RNA. Real-time PCR was performed using Maxima SYBR Green/Fluorescein qPCR Master Mix (Fermentas) with the iQ5 real-time PCR detection system. The relative amounts of target mRNAs were determined using the relative standard curve method and were normalized by relative amount of internal control mRNA. Biological triplicate experiments were performed. FIG. 5 shows changes in MAPKKK18 and RAB18 transcription levels following different chemical treatments in different genotypes.

Example 8: Binding of Cyanabactin in PYR1 and PYL2

Without intending to be bound by theory, subtle changes in the binding pockets of PYR1/PYL2 proteins can dictate the orientation of pyrabactin and contribute towards its selectivity towards PYR1 vs PYL2. In particular, a PYR1^(I110V) mutant dramatically loses pyrabactin responsiveness as compared to wild-type (WT) PYR1. and the reciprocal PYL2^(V114I) mutant gains pyrabactin responsiveness as compared to WT PYL2, while ABA retained responsiveness in all mutants. Cyanabactin's activity was tested with the PYR1^(I110V) and the reciprocal PYL2^(V114I) mutants to provide possible insights into its selectivity for PYR1 vs PYL2.

Recombinant PYR1^(I110V) and PYL2^(V114I) proteins were prepared using a previously described protocol previously (Peterson Peterson, F. C. et al., “Structural Basis for Selective Activation of ABA Receptors,” Nat. Struct. Mol. Biol. 2010, 17 (99), 1109-1113) and tested in absorbance based phosphatase inhibition assay using p-nitrophenol phosphate as substrate as previously described.

Q27 was approximately 9-fold less active in the PYR1^(I110V) mutant with an IC₅₀ of 787 nM as compared to WT PYR1 with an IC50 of 87 nM and was 3.3-fold more active in the PYL2^(V114I) mutant with an IC₅₀ of 981 nM as compared to 3266 nM in WT PYL2 (FIG. 6). These results suggest that Ile110 in PYR1 and Val114 residues in PYL2 were important in contributing selectivity of cyanabactin for PYR1 vs PYL2.

To further gain insights into the probable binding of cyanabactin in PYR1 and PYL2 and rationalize its apparent selectivity towards PYR1 vs PYL2, a model of cyanabactin docked to the binding site of PYR1 (PDB: 3K3K) and PYL2 (PDB: 4LA7) was prepared using Glide. For preparing crystal structures, Protein Preparation Wizard (Schrödinger Release 2015-1: Schrödinger Suite 2015-1 Protein Preparation Wizard; Epik version 3.1; Impact version 6.6; Prime version 3.9) was used with default settings; only the gate-latch water molecule was retained. The Glide settings (Small-Molecule Drug Discovery Suite 2015-1: Glide, version 6.6) were used as default except that “Enhance planarity of conjugated pi groups” was used. The prepared crystal structures of 4LA7 and halo-3K3K (Chain B) were used for docking and posing. Docking poses and hydrogen bond calculations were performed with the UCSF Chimera package.

Cyanabactin and quinabactin had identical calculated interactions in PYR1, with the nitrile nitrogen in cyanabactin and the oxygen of the dihydroisoquinolinone ring in cyanabactin forming hydrogen bond with a water molecule within the “tryptophan lock.” Additionally, hydrogen bonds were observed with Glu 94 and Lys 59 with the sulfonamide linkage in both molecules. The cyclopropyl moiety in cyanabactin and the propyl chain extended into the 3′-tunnel and formed hydrophobic interactions with Leu 87 and Phe 61 and (FIGS. 7A, 7B, and 7C). Molecular docking also revealed that unlike quinabactin, the sulfonamide NH in cyanabactin does not form a crucial hydrogen bond with Glu 98 in PYL2, which may further the rationale for selectivity of cyanabactin for PYR1 vs PYL2. (FIGS. 7D, 7E, and 7F).

Example 9: Growth Complementation and Thermal Response in ABA-Deficient Mutant

The effects of Q27, ABA and quinabactin were assessed in growth complementation and thermal response assays in ABA-deficient aba2 mutant.

For the complementation assay, wild-type and aba2 mutant of Arabidopsis Columbia accession were grown on plate containing 1× MS basal salt mixture, 1% sucrose and 0.4% gellan gum (Gelzan) at 22° C. under the 16/8-h light/dark cycle for 10 days after germination. Seedlings were grown on the pot containing a 1:1 ratio of peat-based, general-purpose growing medium (PRO-MIX BX (Premier)) and vermiculite at 22/18° C., 70/85% relative humidity and 14/10-h light/dark cycle into the plant growth chamber for 5 days. Then 10 mL of 25 μM chemical solutions containing 0.05% Tween-20 were sprayed against plants at daily intervals over a 3-day period five times. Three-week-old plants were photographed and the average rosette area calculated using Image J. Thermal response assays were carried out as described in Example 3. All ligands complemented growth in the aba2 mutants and induced a significant thermal response in leaves of aba2 mutants (FIGS. 8A, 8B, and 8C).

It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes. 

What is claimed is:
 1. An agricultural formulation, comprising a compound of Formula I:

wherein R¹ is hydrogen; R² is selected from the group consisting of hydrogen, fluoro, cyclopropyl, and R⁶; Q is C(R³); A¹ and A³ are independently selected from the group consisting N, C(H), and C(R⁴), wherein at least one member selected from the group consisting of A¹ and A³ is C(R⁴); A² and A⁴ are independently selected from the group consisting of N and C(R⁵); wherein at most two members selected from the group consisting of A¹, A², A³, and A⁴ are N; R³ is cyano; each R⁴ is independently selected from the group consisting of halo, C₁₋₃ alkyl, C₁₋₃ haloalkyl, cyclopropyl, —OR⁶, —SR⁶, and —N(R⁶)₂; each R⁵ is selected from the group consisting of hydrogen, halo, C₁₋₃ alkyl, C₁₋₃ haloalkyl, C₃₋₇ cycloalkyl, C₁₋₆ hydroxyalkyl, nitro, —OR¹, —SR¹, and —N(R¹)₂; each R⁶ is independently selected from the group consisting of C₁₋₂ alkyl, C₁₋₂ haloalkyl, C₂₋₃ alkenyl, and C₂₋₃ alkynyl; Z^(R) is a second ring that is selected from the group consisting of phenyl, naphthyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, pyrrolyl, pyrazolyl, thiophenyl, and thiazolyl; wherein the second ring has from 0 to 5 R⁵ substituents; or a salt or isomer thereof.
 2. The agricultural formulation of claim 1, wherein Z^(R) is phenyl.
 3. The agricultural formulation of claim 1, wherein at most one member selected from the group consisting of A¹, A², A³, and A⁴ is N.
 4. The agricultural formulation of claim 1, wherein the compound of Formula I is a compound of Formula II:

wherein R^(4a) and R^(4b) are each independently selected from the group consisting of hydrogen, halo, C₁₋₃ alkyl, C₁₋₃ haloalkyl, and cyclopropyl; wherein at least one of the R^(4a) and the R^(4b) is not hydrogen; R^(5a) and R^(5b) are each independently selected from the group consisting of hydrogen, halo, methyl, ethyl, trifluoromethyl, nitro, methoxy, ethoxy, and amino; m is an integer from 0 to 4; or a salt or isomer thereof.
 5. The agricultural formulation of claim 1, wherein no more than one ring substituent ortho- to R³ is halo or haloalkyl.
 6. The agricultural formulation of claim 1, wherein no more than one ring substituent is halo, haloalkyl, nitro, or —SR¹.
 7. The agricultural formulation of 1, wherein at least one ring substituent ortho- to R³ is methyl.
 8. The agricultural formulation of 1, wherein the compound of Formula I is a compound of Formula III:

wherein R^(4a) and R^(4b) are each independently selected from the group consisting of hydrogen, halo, C₁₋₃ alkyl, C₁₋₃ haloalkyl, and cyclopropyl; wherein at least one of the R^(4a) and the R^(4b) is not hydrogen; R^(5b) is selected from the group consisting of hydrogen, halo, methyl, ethyl, trifluoromethyl, nitro, methoxy, ethoxy, and amino; R^(7a) , R^(7b), R^(7c), and R^(7d) are each independently selected from the group consisting of hydrogen, halo, C₁₋₃ alkyl, trifluoromethyl, cyclopropyl, nitro, —OR¹, and —N(R¹)₂; or a salt or isomer thereof.
 9. The agricultural formulation of claim 1, wherein R^(5b) is hydrogen.
 10. The agricultural formulation of claim 1, wherein R^(7c) and R^(7d) are hydrogen.
 11. The agricultural formulation of claim 1, wherein R^(7a) and R^(7b) are each independently selected from the group consisting of halo, nitro, C₁₋₃ alkyl, cyclopropyl, —OR⁶, and —N(R⁶)₂.
 12. The agricultural formulation of claim 1, wherein R^(7a) is hydrogen or halo.
 13. The agricultural formulation of claim 1, wherein R^(7b) is C₁₋₃ alkyl.
 14. The agricultural formulation of claim 13, wherein R^(7b) is methyl.
 15. The agricultural formulation of claim 1, wherein each ring substituent ortho- to R³ is selected independently from the group consisting of methyl, ethyl, n-propyl, chloro, bromo, trifluoromethyl, methoxy, and ethoxy.
 16. The agricultural formulation of claim 1, wherein each ring substituent meta- to R³ is selected independently from the group consisting of hydrogen, nitro, and —N(R⁶)₂.
 17. The agricultural formulation of claim 1, further comprising at least one of a fungicide, an herbicide, a pesticide, a nematicide, an insecticide, a plant activator, an herbicide safener, a plant growth regulator, an insect repellant, an acaricide, a molluscicide, or a fertilizer.
 18. The agricultural formulation of claim 1, further comprising a surfactant.
 19. The agricultural formulation of claim 1, further comprising a carrier.
 20. A method of increasing drought tolerance in a plant, the method comprising contacting a plant with a sufficient amount of the agricultural formulation according to claim 1, thereby increasing drought tolerance in the plant compared to not contacting the plant with the formulation.
 21. A method of bringing a plant in contact with an agricultural formulation, comprising contacting the plant with the agricultural formulation of claim
 1. 